Namesakes
Notable Actors and Entertainers:
7 actors, 1 presenter
Pat O'Brien 1899-1983 
Merle Oberon (a.k.a. O'Brien) 1911-1979
Edmond O'Brien 1915-1985
Conan O'Brien 1963-
Kieran O'Brien 1973-
Austin O'Brien 1981-
Dylan O'Brien 1991-
True O'Brien 1994-
Notable Athletes:
1 cricket, 1 rugby
(cricket) Niall O'Brien 1981-
(rugby) Seán O'Brien 1987-
Notable Musicians:
1 singer, 1 singer/musician
Dusty Springfield (a.k.a. O'Brien) 1939-1999
Darrin "Snow" O'Brien 1969-
Notable Writers:
1 author
Anne Rice (a.k.a. O'Brien) 1941-2021
Olympic Medalists:
2 gold, 1 gold/bronze, 1 gold/silver, 1 silver
(silver) Edward O'Brien 1936 4x400 m relay
(gold/silver) Parry O'Brien 1952; 1956; 1960 shot put
(gold/bronze) Ian O'Brien 1964 swimming - 200 m breaststroke; swimming - 4x100 m medley relay
(gold) Michael O'Brien 1984 swimming - 1500 m freestyle
(gold) Dan O'Brien 1996 decathlon
Oscar Award Winners:
1 actor
(actor) Edmond O'Brien 1955 The Barefoot Contessa
Rock and Roll Hall-of-Famers:
2 musicians
Dusty Springfield (a.k.a. O'Brien) 1999
Ed O'Brien 2019 Radiohead
Saints:
1 blessed
Blessed Terence Albert O'Brien 1600-1651