Miles Edward O'Brien is a character in the Star Trek franchise, portrayed by actor Colm Meaney.

However, Meaney came to like the arrangement of being hired on an episode-by-episode basis, and was hesitant to sign on as a regular on Deep Space Nine.

[8] His father, Michael O'Brien, wanted him to play the cello, so he pursued this and was eventually accepted into the Aldebaran Music Academy[9] However, a few days before he was scheduled to start classes there, he enlisted in Starfleet.

[15] Later, he speaks more seriously of fictional ancestor Sean Aloysius O'Brien, a major player in one of the first US workers' unions, who participated in the Coal Strike of 1902 in Pennsylvania and was shot then dumped into the Allegheny River.

[16] O'Brien's first appearance in Star Trek: The Next Generation was in the series premiere episode as the battle bridge flight controller.

[27] For example, he is falsely convicted of espionage and given the simulated memory of a 20-year prison sentence;[28] in another episode, he repeatedly time-travels into the future, witnessing his own death and the destruction of Deep Space Nine.

[29] While stationed at Deep Space Nine, O'Brien meets Dr. Julian Bashir, who initially irritates him,[30] but the two characters eventually become best friends.

[32] After an undercover assignment infiltrating the Orion Syndicate, O'Brien adopts Chester, a cat previously owned Bilby, a man who he grew close to during the mission.

[33] At the end of Deep Space Nine, O'Brien and his family depart the station to move back to Earth, where he is to serve as an engineering professor at Starfleet Academy.

[14] O'Brien is briefly mentioned in Star Trek: Lower Decks as the "most important person in Starfleet history" during a brief cutaway to the far future.

[34] Miles O'Brien of the Mirror Universe was a Terran slave who worked for the Klingon-Cardassian Alliance aboard station Terok Nor.

[36] While he was aboard Deep Space 9, Smiley took the opportunity to download a large portion of the station's database, including the schematics for the USS Defiant.

Eventually, O'Brien receives a distinct senior chief petty officer's insignia, and his rank is emphatically identified.

[39] In interviews, Colm Meaney has praised the writing of the character, and noted "there was a terrific kind of humanity in O'Brien".

[41] In 2012, TrekMovie.com recommended the episode "The Wounded" for Saint Patrick's Day, praising O'Brien's rendition of the Irish ballad "Minstrel Boy".

[42] In 2016, O'Brien was ranked as the 17th most important character of Starfleet within the Star Trek science fiction universe by Wired magazine.

[46] In 2020, Screen Rant ranked O'Brien one of the top five most likeable characters on the Star Trek: Deep Space Nine.