(Sounds like "o-Joe". Or Eau-djeau if you speak French.)
Literally, a formal Japanese word for "young lady", the term Ojou (often Ojou-san or Ojou-sama, as they are the more formal honorifics) is typically used in anime when referring to wealthy, high-class female characters. This is not to be confused with Oujo, which means "princess" or "queen"; ''ojou'' has the accent on the second syllable rather than the first.
This means that while she is often rich, and occasionally even an actual Blue Blood, the key point is that other people treat her like royalty, whether or not she actually is. Sometimes an Ojou can actually attain her status simply by personality alone (often in high school settings where she is probably a School Idol), by being so heavily idolized that a fanclub springs around her, elevating her to a status far above that of those around her, while leveling violent reprisals against any who would treat her as a commoner. Oftentimes, a wealthy Ojou is found in a leading role in the Absurdly Powerful Student Council. In fact, her wealth is often the Hand Wave explanation for the absurd power: they makethe rules because they have money.
Most Ojou characters can be boiled down to three main types, a Proper Lady variety, an Ice Queen variety and a Royal Brat variety. See the Analysis For This Page to see how those three types tend to play out.
Though together for the purposes of this entry, the ojou, or daughter of a high-society family, is written with distinctly different kanji than the oujo, or princess (literally "lord's daughter"). In Japanese, expect all types of ojou to use the more formal first-person pronoun "watakushi" rather than the more casual (and feminine-only) "atashi," and to make heavy use of the "wa" feminine emphasis particle at the end of their sentences.
A staple feature of these characters are to have Ojou Ringlets, Regal Ringlets, or a Hime Cut for a hair cut and for the Royal Brat type a Noblewoman's Laugh.
A character saying "oujo-sama to oyobi" (roughly, "Call me queen") implies something else entirely.
See also Princely Young Man for the Spear Counterpart of this trope. Boys Love works occasionally features a male version of the Ojou.
Setsuna refers to Konoka as 'ojou-sama', as she is the daughter of the head of the Kansai Magic Association.
Also Evangeline, who lives in a gorgeous Big Fancy House and is served by Chachamaru there. She also was a more normal "Ojou", aka a high-ranked membress of a Scottish clan, before she became a vampire by the Lifemaker.
In a throwaway phrase after she gets a Pactio from Negi, Kotaro mentions that Chizuru Naba is an Ojou as well. The Nabas seem to be into heavy industries, so they're are likely to be a part of a keiretsu (the sucessors of the old-timezaibatsu). What does this mean? That her family is on par with Ayaka's in riches and prestige. No wonder they're close friends and share the same dorm.
Confirmed after Ayaka gets her pactio card and explains her business plans to help with Negi's Mars Terraforming project - the Naba's will be helping out financially (which indeed confirms Chizuru's Ojou standing).
Ken Akamatsu's early manga A.I. Love You has two: Kimika Aso is the haughty and mean-spirited type and an Expy of Sayoko Mishima. Cindy McDougal is a beautiful actress whose father is CEO of a major hardware company and a much nicer person, though she doesn't really fit either of the types.
Michiru Kaioh from Sailor Moon is an interesting example of this, in that it is never stated that she is actually filthy rich, and we never have any idea who her parents are, but the fact that she owns a Stradivarius violin and a gigantic condo with its own aquarium (with Haruka) and is a world-famous violinist and painter in her own right (enough so to get double-billing with the world-famous pop sensation The Starlights in the Stars season) still makes her part of this trope. In fact, Usagi, in a memorable episode, wherein she is feeling she is not classy enough or worthy enough of Mamoru, stumbles upon Haruka and Michiru in a theater in a park, where Michiru is up on stage playing her violin and looking classy, and then proceeds to bounce a lemon on her violin while playing it with her eyes closed; Usagi declares Michiru to be the "ideal Princess" and pitifully follows her around for the rest of the episode, hoping she'll get some of it by osmosis or something. Michiru also, notably, has a mirror which always shows her the truth and has the ability to sense when things are coming, and has wavy, aquamarine hair.
It was clearly mentioned in the manga that both she and Haruka are rich, not as much as Hotaru's and Rei's fathers, but had loads of money. Specifically through a good number of patrons.
Rei Hino (Sailor Mars) is also an ojou. She goes to a private Catholic school and her dad's a big politician. Much more in the manga and live-action, though: in the anime, she's alot more Hot Blooded.
Kumiko Yamaguchi in Gokusen is the granddaughter and heir presumptive of a yakuza boss and is called ojou when at home.
Christine "Chris" Robbins from Itazura na Kiss is the perfect example of a non-Japanese ojou. Her mother is a beautiful, famous actress from Hollywood, her father is the president of a major bank, and she has ties with nobility. Charles was even invited to her wedding.
Aeka and Sasami in Tenchi Muyo! both count, though Aeka comes to mind first.
Fujino Shizuru in Mai-HiME, one of the rare ojou with lighter-colored hair.
Reika Ryuuzaki in Aim for the Ace!, one of the founding members of the stylized genre, and the first to use many of the phrases that went on to define the speech of rich girls in anime. (Note that Kazumi Amano Gunbuster is a huge parody of Reika, and indeed Gunbuster is one giant parody of Aim for the Ace!, though few fans are aware of it.
The Macross series possesses a few of these but plays with the trope some. Mylene Jenius in Macross7 fits much of the bill for wealth and eventually quasi-mystical power, but she has an aversion to the responsibility and expectations her social position (daughter of a pair of war heroes) places on her and, aside from her sweet ride, dislikes flaunting her money too much; Sheryl Nome in Macross Frontier is somewhat more traditional, although she usually conceals her identity in public to avoid being mobbed. Interestingly, both possess light hair, Mylene being cotton-candy pink and Sheryl being strawberry blonde.
Actually, the vast majority of characters in the show are this, with Yumi being a notable (and purposeful) exception - even if they don't act the part, all the girls' families are filthy rich. Sachiko is the most extreme example in personality, however.
Yumi is actually turning into the Closer to Earth version of the first type of Ojou. She's definitely got a set of fans that are rabid enough to give Touko hell once it obvious that the latter is being favored by Yumi to be her soeur.
Touko herself counts as a the second type. Even if she's adopted. Actually, the Chinensis family seems to both attract and create Ojous.
Umi Ryuzaki in Magic Knight Rayearth. Fuu Hououji and her sister Kuu also fit the bill, but they're both more modest and ladylike, whereas Umi goes out of the way to make sure we know it and even borders a bit on Rich Bitch at first.
Kurosaki Sayoko and Minazuki Mahiru in Mahoraba. Kurosaki Asami's friend, known only as Sa-chan, tries to portray herself as an ojou as well, but whether she is or not is left an open question in the anime.
In the manga, the answer is revealed. She isn't - she just has a small inheritance and plays up the image in order to get attention.
Kamishirou Rin and Kazetsubaki Kuriko in Maburaho.
Eri Sawachika of School Rumble goes by Ojou to several characters (most frequently Harima). Also a notable Tsundere.
Meiko Akizuki in Marmalade Boy fits the basic character type, though not the full stereotype: she has lighter hair and isn't a member of the Student Council (one of her love interests is the council president, though).
An overseas version of this is Layla Hamilton from Kaleido Star.
A more Tsundere version is Eri Fujisawa, the assistant of the Ryoukufu team in the third Slam Dunk OAV. She's nicknamed "ojousan" by Michael Okita and even by her coach, goes to one really exclusive school for rich kids (lampshaded often in the dialogues) and sometimes is more of a boss than the coach himself..
Aoi Sakuraba, only daughter of a wealthy family, is an almost perfect type 1, and very much the Yamato Nadeshiko. Her bodyguard/tutor/foster-sister Miyabi, a Ninja Maid without the Meido uniform, calls her "Aoi-ojou-sama" from time to time, especially early in the manga.
The perpetually lost Isumi Saginomiya fits the trope even better then Nagi; her profile in the manga even calls her the one most worthy of the title "Ojou-sama", and in the omake to Volume 5, chapter 52, Nagi and Sakuya actually discuss why she qualifies as the most ojou of the ojou-samas. Look it up here and here
The newly introduced Athena also qualifies. Since Nagi and Athena were originally the same character, it makes sense
Athena would fit perfectly, if she'd pull off the laugh.
A rather tragic (and light-haired) Ojou is Hiroko "Hiro-chan" Kaizuka from Narutaru.
Kihel Heim from ∀ Gundam is a blonde, but fits in otherwise. Her little sister Sochie is more of a Tsundere.
Code Geass has two, one on each side of the conflict (though neither one is directly involved in the fighting). Milly Ashford, the president of the school's Absurdly Powerful Student Council, whose family runs the academy everyone goes to. Kaguya Sumeragi was the head of a powerful house in Japan who, despite her young age, is treated much like a princess and has a high social status.
Tatsuki Iizuka from Hyakko, though she doesn't quite give off the Ojou-sama vibe.
Karen Ayanokouji from Akane-Iro Ni Somaru Saka is this type of character. She has the curls, the laugh and tries very hard to please her classmates with her fortune, but ultimately ends up trying way too hard.
She doesn't fit the trope, but it's worth noting that in Hell Girl Enma Ai's assistants always address her as "ojou". (Not usually "ojou-san or -sama", which is odd since she's their boss... but they're all pretty used to each other after centuries together.)
Taiga Aisaka from Tora Dora appears to have the funds—at least enough to live in a huge apartment on her own, financed by her parents (or better said, her mom and stepfather). Of course, her small stature and violent outbursts don't really make her give off the vibe.
Ami Kawashima is perhaps more indicative of this trope.
Tsumugi Kotobuki (a.k.a. Mugi-chan) from K-On! is a light-haired example of the former type.
Sharon Rainsworth, her mother Shelly, and her grandmother Sheryl from Pandora Hearts belong to one of the most powerful families in the series. Oz's younger sister Ada can be an example of this as well.
Ladies Versus Butlers is practically filled with this trope, most of the characters are high class Blue Blood. Sernia Flameheart is at the top of the heap though, with the hair, laugh and (for the first part of the story) attitude, but she lacks the respect of others, who only call her Ojou as a kind of mocking, usually prefering to refer to her as 'Drill' after her hairstyle.
Rodoreamon from Simoun; Neveril is the same archetype but not addressed as such.
Sumire Kanzaki from Sakura Taisen fits the second category to a T. Beautiful, talented and rich, she has no problems reminding others of these facts.
Lucy Heartphilia from Fairy Tail grew up as one but she left because her father focused on his business instead of her to the point of neglect. That being said, no one in the Fairy Tail guild gives her preferential treatment and she prefers it that way.
The all-girl Fujigaya high school from Aoi Hana caters to students from wealthy families, which makes "normal" girl Akira feel out of place at times. Kyouko fits right in though and she also tends to act the part. Yasuko also comes from a wealthy background, but attends the middle-class Matsuoka high school. She is also much more tomboyish.
Mika from Kanamemo is an odd case; she behaves very much like an ojou, even calling Kana a "commoner", but why a rich girl would have to deliver newspapers is never addressed.
Neese in Record of Lodoss War. Her mother is a very high ranking priestess, her father a famous sorcerer, and her grandmother was a one of the greatest heroes of Lodoss. As most kings of Lodoss were born commoners and gained their position by becoming famous heroes, this puts her in the very highest circles of society. Her personal bodyguard Aldo also always calls her Neese-sama.
Midori from Attack Number One starts out as a queenly if not a bit snobbish rich girl on the volleyball team, but progresses into a better sort of ojou who's more on the "graceful and gracious" end.
Cheryl Christina Melville from Tico of the Seven Seas.
Panty & Stocking with Garterbelt has Scanty and Kneesocks, the Evil Counterparts to the heroes. While the main characters are skanky and hedonistic angels who only care about satisfying their base desires, Scanty and Kneesocks are snobby and order-obsessed demons who take their evil duties quite seriously.
Incidentally, an official audio drama done by the voice actors contains the following exchange:
Homura: A hostel? This is my first time. Sayaka: Wow, you’re such an ojou.
Hidamari Sketch: When Yuno and Miyako go to a shrine described as "wonderful" by their teacher, they encounter a Shinto priest who calls them "ojou-san". They soon discover that he calls even elderly women "ojou-san". The two speculate that he's the reason Yoshinoya called it wonderful.
Himeno's two step sisters Mawata and Mayune fit both types of Ojous in Pretear. Mawata is the quiet yet spoiled girl and Mayune is the snarky overbearing type. Interestingly enough, due to her father's remarriage Himeno could easily be an ojou but refuses to let the legions of butlers and maids treat her like one. Or her classmates for that matter.
The Familiar Of Zero's Louise Françoise Le Blanc de La Vallière is stuck in a school where EVERYONE is an ojou (or their male counterparts) because it's a school for royalty. She still expects high class treatment by everyone that's a plebian, ESPECIALLY Saito.
Tsuruya from Haruhi Suzumiya is an aversion to any of the typical personalities. Technically she's an ojou because her family is ridiculously rich, and her Big Fancy House is extremely impressive; however she has absolutely none of the personality traits of one. She's laid-back, down to earth and is simply "one of the girls", not to mention a lot of fun. Probably why she gets along with Haruhi so well.
Yurin L'Ciel from Gundam AGE, who's the Proper Lady type. Unusually for the trope she wasn't born as one, but was adopted by the richest man in her colony after her parents died. Too bad she met a really bad end.
Kagami Kuro from Kodomo no Jikan is the second type but watch for the Tsundere streak.
Chisa Taiami (first type) and Hibari Niigusa (third type) from the post-apocalyptic manga Seven Seeds. Their wealthy families helped fund the Seven Seeds project and insisted that they be included in exchange for this help.
Tsukiko Okakura from Sakura no Ichiban is from a wealthy noble family, has a group of girls that follow her every step, and is a member of the school's Sakura Blossom Club, a club where girls from rich families go to have tea parties. She also possesses a Hime Cut.
Annagramma Hawkin, Tiffany Aching's social nemesis in the young adult Discworld books, embodies the second version of this trope. Slightly subverted in Wintersmith, where it's revealed that her family isn't rich at all and she actually starts to learn from experience.
Live Action TV
Lana Lang from Smallville started out being Smallville's sweetheart. She is kind to everyone, beautiful, and involved in everything so everyone in the whole school knows her and likes her. She also starts out as a cheerleader and the homecoming queen.
Yai in Mega Man Battle Network, a mini-Ojou of the Chiyo-chan sort. Her wealth and connections are often a plot point. They're also how she manages to stay afloat as a NetBattler without her friends' natural talent: she just buys outrageously expensive chips.
Emilie "Lili" de Rochefort from Tekken 5: Dark Resurrection is the daughter of an absurdly rich oil magnate from Monaco that has screw-the-rules money from his franchise (Though, by Tekken 6 that rule seems to have no effect when he was on the verge of bankruptcy). She, however, spends most of her time with her butler, and is quite graceful throughout.
Yukiko Amagi from Persona 4, destined to inherit her parents' classic Japanese inn. She would correspond more to the Type 1 Ojou compared to Mitsuru. Her Social Link is the Priestess Arcana, even.
Lady Riddel in Chrono Cross is a somewhat meek and retiring ojou, though she has her moments of bravery.
Karin Kanzuki from Street Fighter. Despite being wealthy to extremes (she uses her wealth to try to cheat Sakura out of a legitimate competition in the Sakura-focused UDON comic mini-series and can casually arrive to a fight via helicopter), she is talented enough to last in a real fight using her family's martial arts.
From Fire Emblem 8 we have the three princesses of the game: female lead Eirika, her friend Tana, and White Mage L'Arachel.
Touhou's Remilia Scarlet is the Ojou of the Scarlet Devil Mansion. As for influence, well... she IS a powerful vampire... Somewhat subverted in that she's mostly only an Ojou in her own head, and the only ones who actually treats her like an Ojou are her Ninja Maid and, arguably, her librarian.
Also, ghost princess Yuyuko Saigyouji is the Oujo of Hakugyokurou.
And exiled moon princess Kaguya Houraisan is the Oujo of Eientei with Eirin and a horde of rabbits to keep her company.
Sapphire of Disgaea 3: Absence of Justice is an Ax Crazy example of this. Very nice to Almaz though except for one accidental attack and the time he needed to be puched to get him in line.
Yurika Kirishima from Project Justice is an odd amalgamation of qualities from both types of Ojou. Like the Proper Lady, she is unassuming and naive (although her desire for a normal life is to escape her current life as a hired assassin and her brother's reluctant henchwoman), but lacks the vocal fanbase that worships her every move. She has the physical features of the Royal Brat (Ojou Ringlets and Tsurime Eyes eyes), but lacks any of the personality traits of that type. She is still portrayed as high-class and implied to be rich, at least compared to her best friends Akira and Zaki.
Ashelin in Jak and Daxter is the Baron's daughter, a high-ranking member of the Krimzon Guard, and takes over as Governor of Haven City after Praxis's death.
Gardenia from the .hack games both acts like a highly esteemed general and has her own devoted fan club (whom all members refer to her as Lady Gardenia). In fact it's because of Gardenia's fan club that Kite was able to recruit her as they forced him to deliver her a letter. And leading her to reveal she doesn't want anything to do with this fan club when she refuses to cooperate with Kite by taking the letter. At first.
Ridley from Radiata Stories is type 2: A snobby Blue Blood knight, who is followed on her missions by other knights to make sure she doesn't get hurt. After a key event, she mellows into the first type; polite and sweet VIP among her new allies, with an Idiot Hero declaring his life's mission is porotecting her.
Rule of Rose has examples of the both basic types: first Diana who is closer to the latter definition as the de facto leader of the Aristocrat Club, characterized by her strong-willed, mischiveous personality and willingness to humiliate those who don't meet her standards, most notably the protagonist Jennifer. The second example is closer to the first definition: the sickly, gentle-minded Wendy who in her role of Rose Princess outranks Diana and apparently is the founder and lawmaker of the Club. You also don't want to end up in her bad side.
Helena Douglas from Dead Or Alive carries herself as one (and for all intents and purposes, fits the trope) but the soft exterior conceals a very troubled heart.
Arcueid Brunestud from Tsukihime. Very wealthy despite literally having no source of income, presumably based on a fortune that was amassed 800+ years ago. Check. Big house? Castle Brunestud, plus some vaguely alluded to mansions. Check. 'Real' Princess, check. Blond haired, white skinned. No tall dark and bishoujo here. Bit of a lonely rich grown up kid but other than that mostly just a strangely friendly demeanor. Oh, and supernatural powers. Tied to her being a princess in the first place. She's also called the White Princess, if that helps.
Tohno Akiha is a better example, though. She actually does behave like a noble.
Rin Tohsaka from Fate/stay night has at least some characteristics of that: she's from a family of magi nobility (and she's not shy about it), has a large fanclub of boys at school that consider her untouchable.
Shizune Hakamichi from Katawa Shoujo. She comes from a very rich family, lives in a Big Fancy House and is the Student Council President. Later she's revealed to be a Lonely Rich Kid who has driven almost all of her friends away (save for Hisao and Misha) due to how competitive she is, and has very serious issues about it since, being deaf-mute, poor Shizune can't show and express her feelings and thoughts properly.
Lilly Satou could also qualify for this, since she also comes from a rich family and has a Big Fancy House (though she doesn't like it being referred to as a "mansion"). She and Shizune also happen to be cousins.
Ouba Academy appears to mostly be a school for ojous in Kara No Shoujo but the ojou is the local Student Council President, Orihime Tsukishima. Only she's stifling under the atmosphere of the school and expectations on her, so she set up a prostitution ring among those who are similarly repressed.
Black-haired Ayla Goodkind in the Whateley Universe. After being disinherited, she's still worth a third of a billion dollars, which is peanuts by her family's standards. She was disinherited from a mutant-hating family because she manifested as a mutant. She was the blond Sheltered Aristocrat before she manifested.
Solange and Traduce are both definitely examples of the second type. Solange is also the Alpha Bitch.
Asami Sato from The Legend of Korra is the daughter of Hiroshi Sato, the wealthiest man in Republic City and herself a genial, generous fan of pro-bending who talks her father into sponsoring her poor boyfriend's team.
Trixie Tang on The Fairly OddParents is the richest girl in town, and everyone bows to her when she enters the bus (after an introduction said by the bus driver, no less).
For obvious reasons, pretty much every female in the Japanese Imperial Family qualifies as The Ojou. Crown Princess Masako was an atypical case, though, as she had her own career as a lawyer before getting married to Crown Prince Naruhito and, like the Empress, was a commoner.
Western example: Silvia Renate Sommerlath, daughter of a German businessman. She married Carl Gustav XVI from Sweden and is now his Queen.
Another Western example: Catherine, Duchess of Cambridge, who was previously just Kate Middleton.