Miles Edward O'Brien is a character in the Star Trek franchise, portrayed by actor Colm Meaney. O'Brien appears occasionally in all seven seasons of Star Trek: The Next Generation and is a main cast member of Star Trek: Deep Space Nine. O'Brien was originally the transporter chief of the USS Enterprise-D. He was later promoted to chief of operations of Deep Space Nine. Being portrayed in 225 episodes overall, O'Brien is the Star Trek character with the second most appearances in the Star Trek franchise, second only to Worf.

Colm J. Meaney is an Irish actor best known for playing Miles O'Brien in Star Trek: The Next Generation (1987–1994) and Star Trek: Deep Space Nine (1993–1999). He has guest-starred on many TV shows including Law & Order and The Simpsons, and starred as Thomas C. Durant on Hell on Wheels (2011–2016).