Star Crossed Lovers from a ballad, just before his death at her brothers' hands

I lifted her head, she looked at me and said
"Hold me, Darling, just a little while."
I held her close, I kissed her our last kiss;
I found the love that I knew I would miss

—J. Frank Wilson and the Cavaliers, "Last Kiss"

From out of nowhere Falina has found me
Kissing my cheek as she kneels by my side.
Cradled by two loving arms that I'll die for
One little kiss and Falina, good-bye.

—Marty Robbins, "El Paso"

The only kiss that's more meaningful and dramatic than the First Kiss (unless, as is frequently the case, they happen to be one and the same). It's not just the last one we'll see, it's the last one these two characters will ever share... as far as they know at this point, at least. If the characters don't think it could be their Last Kiss, the music and color scheme of the scene will definitely indicate to the audience that it is.

The favorite time to write it in seems to be when one (or both) of the partners is/are on their deathbed (or past it), literally or proverbially, such as just before someone goes off into battle (or their wedding). Possibly will be teary. Less dramatic in old shows where the main character could share one with every new Girl Of The Week or Temporary Love Interest.

May be a Last Request.

See Also: Final First Hug and Go Out With A Smile. Death's the time to show you love someone.

Sometimes overlaps with Dude Shes Like In A Coma.

Not to be confused with Kiss Of Death or Sealed With A Kiss. And definitely not with I Love The Dead. If the characters think it's their Last Kiss but it turns out not to be, it's a Now Or Never Kiss.

Examples:

Anime

Neon Genesis Evangelion: Misato, knowing she's about to die from the bullet wound in her back, kisses Shinji, possibly to snap him out of the near comatose depression he's in.
- It backfires spectacularly as, moments later, Shinji wipes her blood off his mouth and realizes she has probably died.
Ninja Scroll - In the cold universe of the film, where lust, violence and greed has cheapened sex as an expression of love, Kagero's simple kiss for Jubei was an expression of love stronger than any other.
Yoko Ritona from Tengen Toppa Gurren Lagann is a prime example of these, having kissed Kamina and Kittan before both of them died in battle. This is prominent enough for her to earn the Fan Nickname "Doombitch". However, Kittan who kissed her fully knowing he was going to die anyway and apologized for his selfishness.
- Nia's last act before she disappears into nothingness was kissing Simon.
Played straight and subverted in the same episode of Mai-HiME:
- Yukariko and Ishigami share one before they go down together.
- Subverted moments later with Mai just barely missing out on one of these as Yuuichi disappears before their lips touch.
  - That, or he vanished at the exact instant their lips do touch. Either way, she doesn't get to... uh, 'enjoy' it.
Tokyo Mew Mew combines this with Almost Kiss, Final Speech, and Pieta Plagiarism when in the second to last episode Kisshu gets killed trying to help Ichigo.
Subverted in Basilisk. The dying, despaired and insane Kagerou tries to kill a severely injured Gennosuke with her literal Kiss Of Death, but she commits the mistake of briefly looking at her love rival Oboro... who's got the power of neutralizing any ninja's powers. Even more - Oboro had her eyes sealed with some Applied Phlebotinum, but the effect had just worn out as Kagerou was getting ready.
Almost played straight in Bleach where Orihime is given 8 hours to say goodbye to one person before being abducted by Ulquiorra. She enters Ichigo's room. Unfortunately he's unconscious because of a battle, but she says goodbye anyway. She tries to sum up the courage to kiss him, but her insecurities hold her back.
Code Geass has a case of both First Kiss and Last Kiss between Lelouch and Kallen near the end of the show, complete with background music and all. The irony is that while Lelouch really IS on his way to his death and this IS the last thing he does before crossing the point of no return, Kallen initiates the kiss without knowing it at the time.
- Also subverted at the end of season 1 with CC since death is a non-issue for her.

Film

The Postman Always Rings Twice. A kiss in a car, and death follows quickly.
In Pirates Of The Caribbean, Elizabeth shares not one, but four last kisses with different partners: the Kiss Of Death with Jack Sparrow at the end of Dead Man Chest; one with James Norrington when he found out Redemption Equals Death; her wedding-cum-battle kiss with Will Turner; and a forced kiss from Sao Feng. Good thing death isn't always permanent.
- Jack Sparrow lampshades this in the third movie when Elizabeth tries to kiss him, telling her that once was enough.
Neo and Trinity's last kiss before she dies in The Matrix Revolutions.
One such occurrence in Signs is based off an urban legend of a worker at a quarry who falls into the rock crusher and will die soon whether or not he is pulled out or left there, so a third option is taken: he's fed painkillers and his wife is called in who kisses him goodbye and then turns the machine back on.
After Madeleine omniously tells Scottie in Vertigo, "If you lose me, then you'll know I loved you and wanted to go on loving you," she gives him a final kiss before heading off to the clock tower that seems to strangely draw her... Scottie runs after her, but is slowed down by his acrophobia enough to see her plunge to her death from the top of the tower.
Jim and Selena's ...messy kiss from 28 Days Later. It's their third kiss throughout the film- the first was on the cheek and the second was intentional, but this is a full on, Chick Flick Hold, with-tongue affair, sure proof of being doomed. Shortly afterward, he gets shot. Depending on the ending, he usually dies.
In the film version of Death Note, Shiori and Light share a Last Kiss when Naomi Misora shoots her, as a tragic callback to Shiori stating that she would only kiss in public for her Last Kiss. Its a rather dark example since Light used the Death Note to bring about her death, and is exploiting this trope in order to make himself seem genuinely remorseful, as part of his Xanatos Gambit to get onto the Kira investigation team.
This got elevated to somewhat disturbing levels during the Pierce Brosnan James Bond films where he gives the dead Paris Carver a last kiss before he goes and backseat drives in Tomorrow Never Dies, and to Elektra King before starting the final action sequence of The World Is Not Enough. Considering he shot her dead, Bond should logically be giving a smooch to a bloody mess.
The concept is used in The Mask, when the nightclub singer love interest asks her ex-boyfriend for one last kiss before he blows up the nightclub and kills them all. He is so moved by the request that he complies despite the fact that the bomb he planted is already activated and counting down (though it was just a ploy the girl hatched to get him to take off the mask and for her to get it to Stanley).
Dorian: There's ALWAYS time for one last kiss!

Literature

Juliet's final kiss to Romeo before stabbing herself may count, despite that Romeo was already dead.
His Dark Materials: Will and Lyra and their respective dæmons share one final kiss (rushed, clumsy, and tearful) before Will seals their universes apart forever.
In GK Chesterton's The Return of Don Quixote, when John Braintree and Olive admit that their opposing principles mean they should not be a couple, they part after a kiss. At the climax, they realize that their principles can, in fact, be reconciled, so they are reconciled, too.
A Series Of Unfortunate Events had Count Olaf steal one last kiss from his old paramour, Kit Snicket. The two of them then recited poetry while dying from toxic mushroom spores.
In Poul Anderson's The Broken Sword, the dying hero's Last Request is for a Last Kiss.
In Outbound Flight, Jedi Knight Lorana Jinzler and the Chiss syndic Mitth'ras'safis of the Eight Ruling Family, pulling an epic Heroic Sacrifice together, reach out and hold hands for a long moment. It overlaps with Hold Me and It Has Been An Honor, they were on a Full Name Basis since there hadn't been time to exchange first and core names, and both of them were from emotionally cold societies, so exactly what the gesture meant is left to the reader, and some say it was the equivalent of a kiss.

Live Action TV

Doyle kissing Cordelia before his death in episode 8 of Angel.
- Also, Cordelia kissing Angel... after hers.
- And Wesley kissing Fred "please Wesley... why can't I stay"
Buffy kisses Angel goodbye before sending him to hell in the season 2 finale.
In the Space 1999 2nd season episode "The Beta Cloud", a monster is rampaging through Alpha Complex and nothing the crew tries can stop it. Maya and Tony Verdeschi are together waiting for the end when they suddenly start making out (kissing).
In Doctor Who when Jack goes off to die.
- Which of the 5387 separate deaths are you referring to?
  - Unsurprisingly, the first one. Would have sorta lacked punch otherwise.
  - The one where he snogged Rose and the Doctor one after the other. On that note, does the Doctor kissing Rose at the end of the same episode count, even though technically the purpose of it was getting the time vortex out of her head and he was the one who ended up dying?
In Torchwood: Children of Earth as Ianto (and Jack) die.
Chuck and Sara are trapped with a bomb about to go off, and go for what they believe will be their Last Kiss... and then the bomb doesn't go off. Awkward.
- It wasn't even a bomb. It was actually a Human Popsicle box.
Psych has one episode where the wife of a murder victim gives him a Last Kiss at his funeral. It ends up being her Last Kiss as well. She dies in the middle of it.
Lost: Charlie kisses Claire right before diving down to The Looking Glass, which he knows will kill him.
Robin Hood: Kept alive only due to the fact that the sword is still jutting from her stomach,Robin and Marion share their Last Kiss after Guy stabs her. She then proceeds to remove the sword from her abdomen, which does, in fact, kill her.
Battlestar Galactica. Cylon Natalie kisses a fellow Number Six before pulling the trigger on her for killing one of their Colonial allies. Given the nature of the Cylons it's uncertain whether this would qualify as Les Yay or Sister Sister Incest. Also President Roslin has a vision of herself dying in Galactica's sickbay; after her heart monitor flatlines a weeping Adama kisses her, then places his wedding ring on her finger.
Farscape, in the episode "Infinite Possibilities Part II: Icarus Abides". Aeryn and Crichton share a final kiss, shortly before he dies of radiation poisoning.

Music

Richard Thompson's "1952 Vincent Black Lightning" tells the story of a motorcycle-riding outlaw and his beloved, ending with her coming to the hospital and finding him shot and dying. He "gave her one last kiss and died," slipping her the keys to his titular motorcycle as he does so.
Marty Robbin's song "El Paso" (quoted above) tells the tale of a man who loved a dancer in a bar and killed a man who shared his interest. He later runs off into the badlands of New Mexico to escape vengeance from the family of the man he killed only to come back to El Paso and be shot off his horse. Crawling to the door of the bar, the woman cradles him in her arms and kisses him before he succumbs to his wounds.
In the 1960s, "teen tragedy songs" such as the Trope Namer were remarkably popular, including such classics as "Teen Angel" (Mark Dinning), "Patches" (Dickey Lee), "Tell Laura I Love Her" (Ray Peterson), "Leader of the Pack" (the Shangri-Las), and "Ode to Billy Joe" (Bobbie Gentry). Spoofed by Jimmy Cross in a rather shocking manner in "I Want My Baby Back".
Ned and Chuck on Pushing Daisies only got one of these.
Not necessarily an impending death, but still... "Ae Fond Kiss," by the 18th century Scots poet, Robert Burns:
Ae fond kiss, and then we sever;
Ae fareweel, alas, for ever!
Deep in heart-wrung tears I'll pledge thee,
Warring sighs and groans I'll wage thee!

Theater

In Richard Wagner's Die Walküre, Wotan's kiss that strips his daughter Brünnhilde of her powers. The Leitmotif is quite touching.

VideoGames

Subverted in the ending of Final Fantasy X wherein the hero begins losing physical form, so that when the heroine runs after him for the effective Last Kiss she runs through him instead, denying the characters (and the player) a sense of closure.
- He does get to 'hug' her, Having lost his physical form,He puts his arms over her shoulders and holds them there her before he completely fades away.
Star Wars: The Force Unleashed ended its rather unsubtle romantic subplot with this.
- Unsubtle romantic subplots? In my Star Wars!? It's more likely than you think.
  - The Star Wars Expanded Universe is generally held to higher standards than that.

Western Animation

Avatar The Last Airbender: Princess Yue's already in spirit form when she gives Sokka one last kiss before disappearing.
Teen Titans: After several tries, Cyborg finally lets Sarasim kiss him as the two wait to go into battle.

Real Life

Admiral Horatio Nelson, while lying on his death-bed, asked the captain of his flagship, Thomas Hardy, for a kiss before he died. Hardy kissed him twice, on the cheek and the forehead, as a last gesture of affection to the man who had been his mentor and leader for his entire adult life.
- Accounts vary - Nelson's last words may have been " Kismet (i.e. fate), Hardy". But it is also recounted that some of Nelson's captains were so moved by the brilliance of his battle plan for Trafalgar that they wept, so the Kiss Me version has credence.