12 Monkeys: Not only does nobody believe James Cole when he tells people he's from the future and trying to gather information about a worldwide epidemic, but his time-traveling shenanigans and insane rantings may have very well inspired said epidemic to begin with. Reversed by mid-movie; his therapist convinces him he IS an insane homeless person; by the time he tries to seek mental help and turn himself in, she's found corroborating physical evidence (a WWI-era bullet in his body and a history text showing his face in the trenches). She has trouble convincing him he's really from the future. Ironically, said therapist has written a book and given speeches on this trope.
13 Minutes: The Nazis refuse to believe that Elser acted by himself in the attempt on Hitler, despite his story never changing no matter what torture they use.
The Amazing Colossal Man, the driver of a delivery truck asks the soldier on guard duty why he's delivering large quantities of food to the military base. The guard tells him it's for the 30-foot giant they have living on the base; guard replies with a sarcastic "Sure you do" and drives off.
At the end, Patrick calls his lawyer and leaves a message on his answering machine where he tearfully confesses that he has killed 20 or so people, including Paul Allen (whose murder is the most important part of the plot). A few days later he sees his lawyer in a restaurant to go speak to him, and is horrified to find that he doesn't believe him, taking it all to be a strange joke.
In a club, a woman asks him what he does, and he replies "Murders and executions". But it's loud and she's not really listening, so she thinks he said "Mergers and acquisitions".
In fact he confesses everything to lots of people throughout the movie, but everyone's too obsessed with their '80s consumerism to notice. Or, it's all in Patrick's mind.
Patrick Bateman: I like to dissect girls. Did you know I'm utterly insane?
There's a TV Movie called Amos (1985), the plot has a old man in a nursing home with a Nurse Ratched clone who sleeps with a cop and murders the residents when they lose their marbles, so rather than play along he kills himself with the drugs that she used, in a letter to the lawyer exposing her tricks and when a requested autopsy exposes the overdose, the nurse is arrested by her boyfriend and she confesses while protesting the truth.
Another Me: No one will believe Fay that she's got a twin who's impersonating her, since everybody believed (including her) that she was an only child before. Her dad is the only exception.
In the Apocalypse film series movie Tribulation, when Tom Canboro's brother-in-law Jason Quincy (Howie Mandel) is being manipulated by future One Nation Earth agents who want to prevent him from spreading the truth before the world is ready for it, neither Tom nor his wife Susan are willing to believe him due to their past dealings with him that lead to their belief that Jason is mentally unstable. However, Tom's sister Eileen somehow senses that the agent has been in Jason's hospital room and is more willing to believe him, though Tom doesn't believe his sister due to her being a born-again Christian who takes the Bible very literally.
The Babysitter: Killer Queen: Zigzagged. The film begins with everyone at Cole's school thinking he's crazy, after repeatedly trying to tell them that he was nearly killed by a Satanic cult lead by his titular babysitter, Bee. Even the guidance counselor barely listens to a word he says, before dismissing it as pure fantasy and telling Cole he needs to "get laid". But, by the end of the film, his dad and his new girlfriend Phoebe are the only ones who realize Cole was telling the truth all along - having witnessed the deaths of the cultists firsthand.
This is the entire premise of the 1939 Ginger Rogers comedy Bachelor Mother; at the beginning of the movie, Rogers sees a woman abandoning a baby outside an orphanage. Problem is, everyone from the orphanage to Rogers' boyfriend to her landlady and to her boss thinks the baby really is hers, no matter how much she tries to convince them otherwise.
In Back to the Future Part III, Doc Brown has decided to return to 1985 from 1885 and goes to tell his girlfriend Clara the truth about the time machine and when he's from. She is enraged and tells him that it would have been better to just say that he doesn't love her. Also, later Doc tells the locals at the saloon about what life is like in the future, all of it true despite their mockery and disbelief.
In Batman (1989) the first quarter has Alexander Knox being mocked by his peers, as no one (with the exception of Vicki Vale) believed him is his story about a mysterious shadowy vigulante figure roming through the night striking fear into criminals.
Elliot: I'm telling you, the Devil gypped me for a hamburger! Officer: So, do you have a copy of this contract? Elliot: No. I told you, she keeps it in her office. Officer: At this nightclub in Oakland? Elliot: Yes, at a nightclub, and no I can't tell you where it is. Officer: Because you promised the Devil you wouldn't. Elliot: No, because she drove, that's why!
Blind Horizon: The Secret Service puts a man on hold who is reporting a threat to the President? It turns out that they were tracing his call, but they still don't believe him, with his addled state, and he doesn't know what the exact threat is. Also, the doctor speculates "Frank" is making it up from something he read or saw, given his amnesia.
The Burning: Alfred mentions seeing something (who turns out to be Cropsy) by the window of the cabin he and the other guy share, but nobody believes him. Later on, Todd doesn't really believe him either when Alfred tell him he saw Glazer be killed, but Todd does have the sense to at least check it out.
Wait, wait, wait! I have something to tell you. By the time this is over...all of you will be facedown on the floor...and I'll moon-walk out of here. You're not listening to me. First, you're going to help me out of my chair. Then I'll leapfrog over you...before I break his nose. Since my trusty lighter...isn't working, I'll do all this With My Hands Tied behind my back.
Poor, poor Andy just doesn't seem to get a break in the Child's Play original trilogy. He tells people that Chuckie's a killer doll and no one believes him until it's too late. His mom goes through the same thing in the first movie before the main detective believes her after Chuckie tries to kill him while driving his car.
In Choose Me Keith Carradine's character Mickey keeps telling different outlandish stories about his past to other characters and appears to be a compulsive liar. During the movie, the other characters start cross-checking the various different things he's told them and accuse Mickey of lying to everyone. But at the end of the movie, it's revealed that everything he said to everyone was true.
In The Chronicles of Riddick, Riddick tells the prison guards that he will kill one of them with his teacup. The guard, not believing him, rushes Riddick with a knife, and is promptly impaled on the cup. Riddick then places a tin can key where the cup previously sat. The other guards glance at it, then at Riddick, before hastily leaving.
In Cloak & Dagger, from the beginning no one believes David G. Osborne until near the end when his house has been banged up, two dead bodies have been found, and his eight-year-old friend has been kidnapped. Even then, people don't exactly believe him, but they know something is up.
One of Walken's last leading roles, The Dead Zone, is also based around this. He is a Cassandra figure.
In Danish movie "Det Forsømte Forår" the lead character admits, decades after the deed, to murderingthe hated latin teacher. His admission is met by drunken laughter by most of those present except for one who instead expresses regret that he himself didn't do it.
Happens to John P. Merrick in The Devil and Miss Jones when he's caught by the police, pawning his watch so he could make a call to his chauffeur and get him home. They dont believe him since he's wearing a swimming suit (he couldnt find the bathhouse which he put his clothes and rented this swimming suit from), and has no shoes on.
Die Hard has one of the most amusing examples of this trope. Protagonist John McClane is attending a Christmas party on the 30th floor of a skyscraper which suddenly gets taken over by terrorists. He pulls the fire alarm in an attempt to get the attention of the authorities, which winds up being canceled by one of the terrorists. He then steals a radio and tries to contact the police that way. Despite audible gunfire in the transmission, the police dispatcher is still unconvinced and informs John he's broadcasting on a restricted channel, prompting the infamous line, "No fucking shit, lady! Do I sound like I'm ordering a pizza?!" It gets even better when she informs him it is illegal to file a false report and he then begs her to send police to arrest him. According to the script, this scene was inspired by a recording of a real 911 call.
Almost every live-action Disney film ever.
Jack Sparrow even lampshades this in Pirates of the Caribbean: The Curse of the Black Pearl when he tells the two guards exactly why he wants to get onto the ship in Port Royal. He trusts that they will disbelieve him because the truth seems very outlandish and sneaks by them while they're arguing over whether he is or is not lying.
In Pirates of the Caribbean: Dead Man's Chest, Norrington is surprised to learn that Jack was telling the truth about Davy Jones' heart. Jack states that he tells the truth quite a lot, yet people are often surprised. Then Will points out that it's because for all the truth he tells, he still lies a lot. Jack then admits that virtually everything he's told Elizabeth up to that point had been a lie.
Expanded Universe material implies that no one really believed Kevin Flynn from TRON either. Then, he goes missing, and no one thinks to check the arcade for hidden doors...
In A Dogs Tale, the sheriff's deputy continues to scoff at the professor who discovers the wishing star until the professor turns the deputy into a donkey with his one wish.
The opening of Dracula Untold features Vlad and his men coming across what remains of a group of Turkish scouts that have washed down a mountain river. Vlad soon discovers the Elder Vampire, who was the one who slaughtered them when they entered his cave. When the Janissaries arrive in Vlad's court to remind him of his tribute, they bring up the missing scouts, and Vlad replies calmly and honestly that he didn't kill them (without mentioning the true cause of their demise). The Janissaries evidently don't believe him, with their leader even bringing up his past deeds as evidence of his bloodlust.
Mary Smith's employers in the film Easy Living don't believe that a random man threw a sable coat, gave it to her, and then bought her a hat to match.
Referenced by Mike in Eight Legged Freaks. After escaping the giant mutant spiders' lair and coming across the town sheriff, he is reluctant to tell his story. This is with physical evidence of a giant spider leg that he managed to take with him. After much prodding, he eventually provides a long-winded, detailed explanation of the trope along with what he saw. To his annoyance, he predictably isn't believed.
Chris at one point calls while on a radio antenna while Harlan defends him. They continue firing at the spiders as they approach while Chris desperately tries to get some response from the 911 operator and begs for help from the military. Obviously she doesn't believe him about and invasion of giant spiders and hangs up.
Endless: No one believes that Riley is really speaking with Chris. They just think it's hallucinations due to her grief at his death, and are quite concerned as a result.
Fabian figures out the Adolf Hitler he has been spending time with and has helped become a media sensation is the real Adolf Hitler, instead of just a particularly talented comedian who refuses to ever break character like everyone assumes. He ends up in a straitjacket and padded room when he tries to convince others.
Franziska's grandmother, having experienced WWII and its horrors herself, correctly assumes she's dealing with the real Hitler and tries to convince her granddaughter of this. Because she is senile, Franziska treats this as a delusion and explains that its just an actor in a comedy, after which her grandmother angrily states the real Hitler was also treated as a comedic character before his rise to power.
In a bit of dark comedy, Hitler himself never denies he's Hitler and even proudly proclaims it at certain moments, yet no one believes this and he keeps being treated as a comedian who never breaks character.
The Invigilator in Exam, technically. He only said that he was going to ask them one question; no one believed him.
Fear, Inc.: Joe's Nosy Neighbour Bill, who is the captain of the local neighborhood watch, warns Joe about a van he saw parked in front of the house and that he thinks someone has been on the property. Joe brushes him off because Joe's a Jerkass. Turns out, he should have listened to Bill.
In Ferris Bueller's Day Off, the police unaccountably don't believe Jeannie when she calls about Rooney breaking into her house.
Averted in Fight Club, where the Narrator tries to confess his alter ego's crimes, and is believed, only to realize that everyone in the room is in on it.
A common theme in the Final Destination series. Frequently, the initial visions of the hero are only believed by a small number of people. The hero will then try to warn people about death's machinations but will be ignored.
The 1994 war film Forrest Gump uses this when Forrest's revelation that he's the owner of the wildly successful Bubba Gump Shrimp Company sends one listener off in unbelieving hysterics. The old woman was unbelieving at first, until he shows her a picture of him and Lieutenant Dan on the cover of Fortune.
In Fright Night (1985), Charley sees his neighbor Jerry grow some fangs and the drink the blood of a helpless lady, so he starts yelling at his mom and friends that Jerry is a vampire without any evidence. Then he calls his police and tells them that the lady was murdered by Jerry, but when the police find problems with Charley's story he immediately falls back to the vampire explanation.
The Fugitive: Richard Kimble's story of a one-armed breaking into his house and killing his wife. The cops clearly don't believe him from the get-go (in all fairness, in such an investigation, the husband is the prime suspect), and the bizarre detail such as the attacker being a one-armed man all but confirm their (inaccurate) suspicions.
In Ghostbusters II, the attempts of the Ghostbusters to warn the mayor that a demonically possessed painting is plotting to destroy the city at 12:00 AM New Year's Day sees them institutionalized, which given how they were right about the events of the first movie, may seem a little harsh (although it was partly due to the machinations of the mayor's scheming aide). In a minor subversion, Peter — who sees that his colleagues' attempts to struggle against their captors whilst ranting about demonic paintings and the end of the world just makes them look even crazier — merely goes along with it in a calm and reasonable fashion until someone wises up and lets them go.note He also knows to appeal to the mayor's political side by claiming that, if they succeed, the mayor will have been partly responsible for saving millions of registered voters.
Peter Venkman: Don't look at me. I think these people are completely nuts.
In Ghost Rider, Johnny Blaze awkwardly explains to his Old Flame Roxie that he is the devil's bounty hunter, which she believes is merely a ridiculous excuse.
The Good Son revolves around this trope, with the protagonist attempting in vain to warn his family of the homicidal nature of his cousin. The movie was loosely based on the novel The Bad Seed, which also had a Cassandra Truth plot to it.
Chloe tells Miranda she is being raped by "the Devil". Miranda naturally thinks this is a delusion (although still based on really being raped by her stepfather in the past). However, it turns out that "the Devil" is her term for a very real man she's being raped by. Miranda later apologizes for not believing Chloe.
Miranda may have killed her husband, but she wasn't crazy; she was possessed.
In the Gremlins series, the authorities do not believe that a horde of little monsters that can't be fed after midnight are terrorizing the local movie theatre and sporting good store.
In Grosse Pointe Blank, Martin Blank tells everyone at his class reunion up front that he's an assassin, and everyone assumes he's joking. That is, until he is found having killed another hitman using only a pen.
His girlfriend's father: Good for you, son, it's a growth industry.
In the Halloween series, Dr. Loomis' entire career in regards to Michael is this. No one ever listens to his warnings about the danger Michael poses to society... even after the dead bodies start piling up.
In Hangmen Also Die!, Czaka tells the Gestapo that he's innocent and that the Resistance is framing him for the assassination of Heydrich. That is precisely what's going on, but the frame-up is successful regardless.
In Happy Accidents Sam tells a group of people, including a famous actor, what the future is like. They take it as improv.
The Spanish film Hasta la lluvia ("Even the Rain") revolves around a film crew that goes to Bolivia to make a movie about Christopher Columbus because it will be cheaper to film there. When the director views the casting footage, he asks that they cast a specific man as the role of the Indian chief because of the way he riled the crowd who was asked to leave after they waited for several hours for the chance to be cast in the film. The executive producer warns the director that man will be trouble, but the director just says that event showed that he's a natural leader, and he's cast as the Indian chief. The producer was right, the actor spends his time between film shoots protesting the government's decision to sell the water rights to a multinational that holds exclusive rights to all of country's water,even the rain water that collects in empty containers belongs to the multinational.
Hazmat: When Ed returns to the warehouse after Jacob's gone crazy, the others contact him over the radio to warn him. Ed just assumes that they're pulling a behind-the-scenes prank on him, and doesn't believe their warnings.
The Hidden: The good alien is more than aware of this and prefers to keep his human partner out of the loop concerning the body-jumping alien parasite they're both pursuing. When he does finally tell him the truth about space aliens after his cover identity is exposed as a fake, he is thrown in a jail cell because his partner thinks he's pulling his leg.
In The Hobbit, Gandalf and Radagast are convinced that the Necromancer is Sauron or at least someone as dangerous as him. But of the other White Council members, Saruman is not convinced and Elrond is powerless to do anything. Galadriel is the only one to avert the trope; she senses something genuinely sinister is happening and puts her faith in Gandalf.
In Home Alone 3, the cops don't believe Alex's claims that burglars are breaking into neighborhood houses. Somewhat justified in that the cops came in three times. It's just that the industrial spies breaking in to houses were pretty good at running away and leaving no traces. Alex doesn't even bother calling them when the burglars come for him, realizing that he's cried wolf too many times. And yet, the cops do eventually show up, because of a call he made earlier to an army recruiting station.
Home Sweet Home (2005) revolves around a family who recently moved into a high-rise apartment block, and shortly afterwards finding out about an urban legend of a child-kidnapping "monster" living in the basement. The family's young son is the first to actually witness the "monster", but is unable to convince his parents about it (what with the father remarking that the boy is only stressed out because of the moving process).
In The Host, nobody but Gang-du's family believes that his daughter is still alive after being taken by a giant monster from the Han.
House Shark: Naturally, nobody believes Frank when he says that there's a monster in his house. And of course, they ALSO don't believe him when he says that it's a house shark.
David figures out the aliens have embedded their countdown to destroying humanity in the global satellite network. His coworker believes him but is panicky and in no condition to do anything. David's father believes him and takes him all the way to Washington DC, where David's ex-wife blows him off thinking him paranoid. But David is right, and his father wastes no time in reminding people who try to treat David like an idiot. It's really a subversion, because when the president hears him, he believes him immediately.
Russell Casse suffers under this every time he talks about being abducted. He even elicits eyerolls from Major Mitchell when he mentions it at the pilots' briefing before an attack on the HUGE ALIEN SHIP! Even so, it is left ambiguous as to whether he actually was abducted by the aliens or was simply crazy. The eyeroll can be seen as a reflexive reaction from someone who had just learned aliens were really real a couple days before. The way Russell says, "I'M BAAACK!" would imply he believed what happened was real.
In The Intruders, Rose tries to convince her father that there is someone hiding in the old house they relocated into. Her dad dismisses her as developing the same illness that plagued Rose's mom. The villain is indeed hiding in the house's deep basement.
Jennifer's Body: Chip initially doesn't believe Needy's seemingly outrageous claims about Jennifer, not that you can blame him. Also, Needy is the only one who knows that Low Shoulder aren't the heroes everyone else thinks they are; no-one else believes her when she states otherwise, presumably because that's part of Low Shoulder's Deal with the Devil, or they'd just garnered a good reputation by (allegedly) saving people from the fire.
Dr. Ian Malcolm in the first two Jurassic Park movies, but the second in particular; the only character present who experienced what could go wrong when humans and dinosaurs interact, his warnings only seem to be finally taken seriously when the two tyrannosaurs attack the camp, much to his irritation and, well, too late. No amount of Cassandra Truth stops Malcolm from remaining a Jerkass.
Kick-Ass: Frank's guys saying they got robbed a man in a costume isn't believed early on, resulting in him punishing them horribly.
Played for laughs in Killer Klowns from Outer Space: In most of the movies on this page, the police refuse to believe that something is going on because the only person telling them is some random nut. In this movie, however, everyone in town calls the police to report the strange goings-on. The police decide that everyone in town must be pranking them.
In King of the Zombies, everything Jeff tries to tell Mac and Bill about the existence of the zombies and the voodoo cult is proved to be absolutely true. However, the white 'heroes' dismiss him out of hand as he is the black Comic Relief, and do not believe in the zombies until they encounter them themselves.
Kiss of the Damned: Paolo, as you might except, reacts with laughter first when Djuna says she's a vampire. He believes it upon her displaying a game face however.
In the original The Ladykillers (1955), the old lady tells the police she's got the money from the robbery but the robbers have mysteriously vanished. The constable, thinking it's another of her crazy dreams tells her she can keep it — much to her surprise and delight.
In The Ladykillers (2004), the old lady tries to tell the police that she's found the money from the casino robbery, but the cops don't believe her, instead telling her to donate the money to Bob Jones University.
The Lady Vanishes has shades of this early in the second act, as Iris tries desperately to convince everyone that Ms. Froy (the eponymous vanished lady) really exists.
Licence to Kill: After James Bond performs a death-defying stunt to steal Sanchez's money, Krest tries to explain what happened to Sanchez. Sanchez finds the story too far-fetched, saying there's no way someone would be able to do that, and accuses Krest of stealing it himself. Unfortunately for Krest, Bond then frames him by planting some of the money at his boat, causing Sanchez to kill him.
In The Mad Miss Manton, Melsa Manton finds a dead body, calls the cops, but then it disappears, so they think shes crazy at first, but then a prankster because shes prankster, Melsa Manton.
Maleficent: Mistress of Evil: The reason Diaval wasn't trapped with the other non-human guests at Phillip and Aurora's wedding is because the guards don't believe he's a raven in human form.
Boris: Who you are working for? Wallace: Blockbuster Video, Des Moines, Iowa. Boris: Who you are working for? Wallace: Blockbuster Video, Des Moines, Iowa. Boris: Damn, they trained him so well.
In Midnight Movie Timmy tries to tell the police about the events that occurred in the theater but no one believes him.
In Mr. Right, Francis meets Martha and pretty blatantly tells her he's a former contract killer and people are out to kill him; he even interrupts a date to go kill someone outside and tells her exactly what he was doing. These aren't things most people would casually admit to, and Francis generally comes off as a Cloud Cuckoolander, so she just thinks he has a weird sense of humor and plays along. When she learns it's true, she's understandably upset and accuses him of lying; he reminds her he was telling her the truth the whole time (part of why she forgives him so quickly).
Monty Python and the Holy Grail: "I warned you but would you listen to me? Oh, no. You knew it all, didn't you? It's just a harmless little bunny rabbit, innit?"
A 1980's Disney kid's ghost film Mr. Boogedy used this trope in the first film ("Kids, ghosts just don't exist, you're imagining things"), but reached facepalm dimensions in the sequel ("Kids, we sealed the ghosts in the 9 pits of Hades, they can't be back, you're imagining things")
The police refuse to investigate the two dead bodies in Mystery Team, simply because the main character is an amateur detective.
National Treasure: Ben Gates warns the FBI, the DHS, and the National Archives that someone will steal the Declaration of Independence, but they all dismiss him as crazy. When it is stolen, an FBI agent has to sheepishly admit to his superior that they had been tipped off and ignored it.
Agent: There was no file opened; we didn't find the information credible.
In Nighthawks a handsome man picks up a stewardess and goes home with her. She asks him what he does as his profession, and he tells her the truth. "I'm an international terrorist wanted in 19 countries." "Well, maybe someday you'll quit the jokes and tell me what you do for a living."
It's a recurring theme in the A Nightmare on Elm Street franchise, for obvious reasons. No one except other teenagers is willing to believe that an undead serial killer is haunting their dreams.
In A Nightmare on Elm Street (1984), no one believes Nancy when she tells them someone is after her in her dreams. Double subverted in that it's later revealed they are fully aware who Freddy Krueger was and that they personally buried him after he murdered their children, they just don't believe he could come back from the dead.
Done to the most deadly effect in A Nightmare on Elm Street 3: Dream Warriors where the survival of teenagers against someone in their dreams is set in a psychiatric facility. The teenagers now have to get around the stringent rules and regulations of the staff as another obstacle whilst trying to defeat their worst nightmare who is actually real and trying to kill them, but since other people can't see Freddy as he exists in dreams, they are deemed delusional and end up sedated. This is the opposite of a good treatment concerning the aforementioned danger it puts the teenagers into, despite the fact many of the staff actually want to help the teenagers but just don't understand the root of the problem. This lack of understanding, however friendly, can end with death.
Early in Night Watch (Series), a police officer asks Anton if he's been drinking, and Anton says "only blood". The cop doesn't believe him — at least until he starts vomiting it up.
In Now You See Him, Now You Don't, after Dexter and his friends discover that A.J. Arno and his flunkies plan to use the stolen invisibility formula to rob the bank and make the money invisible, Dexter and Schuyler try to warn the bank president and the police about this, only to be blown off about it, until the crime has actually been committed.
Nobody, not even her husband and therapist, believed Kate's accusations of sweet seemingly nine-year-old Russian Orphan Esther actually being a murderous psychopath.
In Overboard (1987), when Annie finds some panties in the glove compartment of Dean's pick up truck, she accuses him of cheating on her, which he decides that this is the right time to come clean about everything that's happened. He goes on to tell her that she's an heiress worth millions of dollars, he's just a carpenter, not her husband, and his three sons are not hers. When she doesn't believe him, he tells his sons to back him up, but they say she is their mother. Dean's friend Billy "confesses" that the underwear belong to his girlfriend, and forgot them when he borrowed Dean's truck to go on a date.
In the 2018 remake, Leo finds a bunch of condoms in the glove compartment of the car and accuses Kate of cheating in him, which she decides to just come clean and confesses that they are not married and her three daughters are not their children, when Leo doesn't believe her, she asks the girls, who say he is their father. Her friend, Theresa, "admits" to cheating on her husband, and leaving the stacks of condoms when she borrowed Kate's car.
The Parallax View: Nobody (including Frady) believes Lee's story until she dies herself.
The Poltergeist remake has Griffin, the son, trying to warn the family about the weird stuff happening in the house. Not only does the family not listen to him, the mother suspects that he might be suffering from mental issues and is willing to send him away for professional help.
Inverted by The Professional - Mathilda's cover story to the headmistress of a school for troubled girls isn't believed because it's too generic, but she's believed when she reveals she's the Sole Survivor of a family murdered by a corrupt DEA agent who was adopted by an assassin.
In Robot Holocaust, Valeria tells The Dark One that the power source has been compromised but the latter doesn't believe her (despite being dependent on said energy...again, the screenplay is poorly thought out).
In the Hitchcock film Saboteur, the protagonist flat-out tells the crowd what the big bad's plan is at a high society party and the party goers find him amusing and laugh along.
Salvation Boulevard: Carl finds his wife and father-in-law both refuse to believe what Jerry did. He also was warned by a security guard not to speak with the police, since half are Pastor Dan's parishioners, so they might arrest him for shooting the professor. Eventually though his father-in-law grows suspicious and realizes Dan is lying.
The Secret (2007): No one believes Hannah is trapped in Sam's body at first. Over time Ben realizes it's true, but they don't try to convince else, as obviously they realize it would just cause problems, and act like Hannah is Sam.
In Silver Lode, Ballard maintains his innocence, but the townspeople gradually turn against him and start believing McCarty's account of the events instead.
In Small Soldiers, Christy tells the police about the attacking action figures. The police don't believe her, at which point she realizes that they will come to the house anyway to arrest her for making a prank call. Instead, they hang up.
In Sodom and Gomorrah, Lot attempts to warn the Sodomites that their city will be destroyed by Jehovah's divine wrath unless he can find ten righteous men among them to lead away along with his fellow Hebrews. He is greeted with derisive laughter and, from one Sodomite, the contents of a goblet of wine to the face. Sure enough, when the last Hebrew leaves the city, the lightning storms, earthquakes, and fiery explosions begin, and everyone left in the city is killed.
Spotlight has Real Life survivor of clerical abuse Phil Saviano, who reported the rampant abuse to the Globe years before the events of the film but was not taken seriously. When Pfeiffer tells the rest of the Spotlight team that she plans to interview him, they're very skeptical because of his zeal. Naturally, as it becomes more obvious that he was telling the truth, he's very frustrated that it took everyone that long to listen.
In Star Trek IV: The Voyage Home, Admiral Kirk reluctantly explains to Dr. Taylor that the reason he needs her whales is that he's a time traveler from the future. Naturally, she thinks he's nuts. (This is understandable, because Kirk does only a passable job of blending in to the 20th century.) Eventually circumstances force her to turn to him as her last resort, proving once again that if it's crazy but it works, it's not crazy. When the subject is first brought up, it's kind of funny:
Taylor:(after Kirk tries to broach what is obviously an awkward subject) Don't tell me. You're from outer space. Kirk:(oozing charm) No, I'm from Iowa. I just work in outer space.
In First Contact, Commander Riker and Troi have traveled back to 21st Century Montana and try to convince Zefram Cochrane, inventor of human warp flight and the man responsible for humanity meeting the Vulcans, of the importance of his flight, and why the Borg are trying to stop him.
Cochrane: So... lemme just make sure that I understand you correctly, Commander. A group of cybernetic creatures from the future have traveled back through time to enslave the human race, and you're here to stop them? Riker: That's right. Cochrane: Hot damn! You're heroic! (laughs in Riker's face)
In Star Trek (2009), Kirk attempts to get Pike to stop the Enterprise as he's put two and two together and realized the ship that destroyed the U.S.S. Kelvin is at Vulcan and is the cause of the "natural disaster" on the planet. However, seeing as this was done after Kirk's little Kobiyashi Maru stunt, Pike doesn't believe a word he's saying and Spock is more than happy to want to toss him out of the bridge on his ass. However, when Uhura starts to back up his claims, Pike at least has the sense to raise shields and go to red alert. However, Kirk's claim ultimately is proven true when they drop out of warp and they're greeted with the debris field that was once a fleet of ships.
In a word, Darth Vader. He had serious doubts that the Death Star was as invincible and foolproof as everyone thought it was, and while he might have had more success convincing the Rebellion about that, the warning he gave in this scene was ignored by everyone listening (not just Admiral Motti, who Vader infamously had to Force-choke into line to prove a point):
Vader: Don't be too proud of this technological terror you've constructed. The ability to destroy a planet is insignificant next to the power of the Force.
And in the same movie there was the scene during the Battle of Yavin where Moff Tarkin brushed off an advisor's suggestion that the Rebellion's attack actually posed a danger, and refused to consider having his escape craft prepared. He paid for that mistake with his life. Vader took the threat seriously when Tarkin wouldn't. He tapped two TIE fighter pilots for wingmen and delved into the dogfight himself in attempts to thwart any more runs on the exhaust port. Naturally, his foresight made him one of only two survivors of the Imperial Forces in that battle (other than five defectors who escaped before it was destroyed).
In Attack of the Clones, this is invoked by Count Dooku, who tells Obi-Wan that the Republic is under the control of a Sith Lord named Darth Sidious. In this case, the audience is aware that Dooku is telling the truth, while Obi-Wan doesn't believe him. At the end of the film, Obi-Wan tells the other Jedi Masters about this, and Yoda immediately says that Dooku is probably trying to create mistrust among them, and they shouldn't take his words at face value. What Dooku didn't tell Obi-Wan is that Sidious is alsobehind the Separatist movement, and that he himself is Sidious's student.
Jack: Oh... I had a date tonight, so I had to call and cancel... Cabot: Well, don't be stupid! Tell her where you're going. In fact, tell her who you work for. She'll be impressed. Jack:(to Cathy, over the phone) OK. I work for the CIA, and the Director asked me at the last minute to come with him to Russia with him to do a nuclear arms inspection. Hello? Cathy: That is so lame. (she hangs up; Cabot and the other experienced CIA officers laugh)
In The Terminator, the psychologist doesn't believe Reese's story about the future and deems him a paranoid schizophrenic. Neither do the police believe that the murderer (whom they believe is merely a drugged-out psycho with body armor) will "wade through them to kill Sarah". The Terminator does exactly that about five minutes later, killing 17 police officers including Ed and Hal.
Sarah Connor started out Terminator 2: Judgment Day in an institution for largely the same reasons after being caught trying to blow up a Cyberdyne facility, although admittedly she didhave actual issues by that point. In one cut of the film, we see the therapist carted off in a straitjacket and ranting madly after witnessing proof of Sarah's "delusions" come after her.
In Terminator 3: Rise of the Machines Dr. Silbermann from T2 has a rant about seeing impossible things indicating he no longer even believes his own memories, then freaks upon seeing the Terminator validating his own memories of events.
They Live! has the protagonist stumble upon a plot to keep humanity under the control of an alien race. Surprisingly he only tries to tell one person, his only friend, who believes he has lost it. Not helped by the fact the two end up in a fist fight over him insisting the friend put on a pair of magic sunglasses. Eventually he does and the two spend the rest of the movie fighting against the invaders.
In Tin Cup, Molly doesn't believe Roy that her fiancee David is an asshole who hates "old people, children, and dogs", thinking it's just sour grapes she's dating Roy's long-time rival. She leaves him for Roy when she sees David display his dislike for all three at once.
Troll 2: Nobody believes Joshua about the goblins until it's too late.
Inverted in Troy. The priests always give the wrong advice, and are always believed.
Played straight when first Hector, then Paris call the priests out for their bad advice, and are ignored. Particularly when Paris warns his father not to take the horse into the city.
In True Confession, Helen is a pathological liar, so her husband doesn't believe her when she says that she didn't kill a man. She's innocent, but since he doesn't believe her, she plays along with his theory of why she killed the man.
Played with in True Lies, where Arnold's character has been placed under the effects of a Truth Serum whilst handcuffed and immobilised. He's half-drunk from the drug, and the doctor administering the truth drug begins to ask questions...
Samir: Now, then, is there anything you'd like to tell me? Harry Tasker: Just that you're going to be dead soon. Samir: Really? Harry Tasker: Yeah. First I'm going to grab you, and use you as a human shield, then I'm going to kill this guard over here with the Patterson trocar on the table. And then I was thinking about breaking your neck. Samir:(smiling disbelievingly) And how is that going to happen? Harry Tasker: You know my handcuffs? Samir: Yes? Harry Tasker:I picked them.(holds up the handcuffs; events transpire as predicted)
Ultraman Cosmos: The First Contact: Haruno Musashis attempts to convince his parents and classmates that he met Ultraman Cosmos in the woods is met with ridicule and laughter. It doesnt help that the mystical blue stone Cosmos had given him after the meeting disappears on its own in crucial times.
In The Wedding Date, Debra Messing's character hires a gentleman escort as her date, so that the rest of her family and her ex-fiancé will be jealous. Later, when the groom asks him how he knows so much about women:
Nick: I'm a hooker.
The Whole Town's Talking: Jones looks so much like the gangster Mannion that the police don't believe him when he assures them he's not the notorious gangster.
When he's first sent back to the '70s in X-Men: Days of Future Past, Wolverine wakes up in the bed of a mob boss's daughter who he has apparently slept with repeatedly, and her father's goons aren't happy. He quickly lampshades that they probably won't believe that he's traveled back in time.
In Zenon: Girl of the 21st Century, the title character stumbles upon the suspicious activity of a Corrupt Corporate Executive that is later discovered to be an upload of a computer virus that would disable the life support systems of the space station she lives on. But nobody believes her and she is banished to Earth for having snuck into a restricted area. She tries to make it back to the station to warn everyone and fix the problem before it is too late.
In Zombi 3D, we get this little gem from General Morton as his soldiers burn someone infected with the Death One virus:
Dr. Holder's Assistant: Hadn't it ever occurred to you that the ashes, assimilated into the air, could fall back to Earth again? General Morton: That's ridiculous, pure Science Fiction!