List of Marvel Comics characters: O

Rose O'Hara is a fictional character appearing in Marvel Comics. She first appeared in Origin #1 (September 2001), and was created by Bill Jemas, Paul Jenkins, Joe Quesada and Andy Kubert. She is a friend of Wolverine. An orphan servant on the Howlett estate in the late 19th century located in Alberta, Canada, Rose is a friend of James Howlett. She had to deal with Dog Logan making unwanted sexual advances toward her before James foiled Dog's attempt by Dog to assault Rose sexually, ultimately resulting in Dog's expulsion. Rose later witnesses Dog and Thomas Logan try to take Elizabeth Howlett and accidentally kill John Howlett, Jr. to which James uses bone claws against Thomas and Dog, resulting in Thomas's death and Dog's face being slashed severely. James runs away with Rose pursuing while Dog fraudulently-reports to the police that Rose was responsible. Rose and James travel to the north of Canada, ending up in a small mining community deep within Canada; Rose claims James is her cousin Logan and the two settle. Rose had a journal by hand in which she had described the events of her life. After several years, James feels very attracted towards Rose but these romantic feelings are not mutual. Rose falls in love with Brendan "Smitty" Smith and they make plans to marry much to James's grief. However, Dog had tracked the pair down and the brothers fight; Rose tries to intervene and is stabbed and killed accidentally when she falls onto James's claws.

Rose O'Hara appears in Wolverine Noir.

Blackjack O'Hare is a fictional anthropomorphic hare in Marvel Comics. The character, created by Bill Mantlo and Sal Buscema, first appeared in The Incredible Hulk #271 (May 1982).

Blackjack O'Hare is a mercenary and leader of the Black Bunny Brigade. He was hired by Judson Jakes and Lord Dyvyne to kidnap Lylla, the C.E.O. of Mayhem Mekaniks. He planned on betraying his employers by marrying Lylla and inheriting the company, but was found out. He was rescued by Rocket Raccoon and after a series of incidents that caused him to question his own loyalty, he aided Rocket in defeating the tyrants and left with his new friends to start a new life.

All this appeared to be false when Rocket visited Halfworld and discovered that Blackjack, along with Lylla and Wal Rus, were originally service animals for the mental patients who inhabited the planet. Blackjack married Lylla after Rocket left to ensure the imprisonment of a dangerous criminal. However, this story was retconned as Blackjack later returned as a mercenary and adversary to Rocket and Groot.

A character based on Blackjack O'Hare named Floor appears in Guardians of the Galaxy Vol. 3, voiced by Mikaela Hoover. This version is a white rabbit who was experimented on by the High Evolutionary and possesses genetic and cybernetic enhancements. She is killed by the Evolutionary during a failed attempt to escape his captivity, but reunites with Rocket during a near-death experience that he has.

Oblivion is a cosmic entity associated with the concept of the primordial void that the Marvel Multiverse sprang from and will eventually return to.

Harry Ocelot is an anthropomorphic ocelot and animal version of Harry Osborn.