John O'Brien
John O'Brien may refer to:
Public officials
American
- John O'Brien (Ohio politician), former member of the Ohio House of Representatives
- John D. O'Brien, state senator in the 1997–1998 Massachusetts legislature
- John F. O'Brien (secretary of state), Secretary of State of New York, 1903–1906
- John F. O'Brien (judge), New York Court of Appeals judge
- John H. O'Brien, 4th Fire Commissioner of the City of New York
- John J. O'Brien (civil servant), investigated the assassination of President John F. Kennedy
- John J. O'Brien (commissioner), former commissioner of the Massachusetts Probation Service
- John P. O'Brien, 98th mayor of New York City
- John L. O'Brien, American politician in the Washington House of Representatives
Irish
- John O'Brien (bishop), Irish Bishop of Cork and Cloyne
- John O'Brien (Irish politician), MP for Limerick City in the UK Parliament 1841–1852
- John O'Brien (priest), Irish Roman Catholic priest and musician
- John Thomond O'Brien, Irish soldier in the Argentine War of Independence
- Joseph O'Sullivan, who assumed the name "John O'Brien" while under arrest for the 1922 assassination of Sir Henry Wilson
British
- John O'Brien (British politician), far right figure, onetime leader of the British National Front
- Sir Terence O'Brien (colonial administrator), British surveyor, engineer and colonial governor
Canadian
- John O'Brien (admiral), commander of the Royal Canadian Navy
- John O'Brien (Canadian politician), merchant and member of the Legislative Assembly of New Brunswick
New Zealand
- John O'Brien (New Zealand politician), New Zealand political candidate and party leader
Australian
- John O'Brien (Australian politician), Member of the Queensland Legislative Assembly
- John O'Brien (Australian Army officer), Australian major general and Mayor of Woollahra
Sportspeople
Baseball
- John O'Brien (outfielder), baseball outfielder
- John O'Brien (second baseman), baseball infielder
- Johnny O'Brien, 1950s baseball second baseman
- Cinders O'Brien, baseball pitcher
Footballers
- John O'Brien (Dublin footballer), senior inter-county Gaelic footballer for Dublin and Round Towers, Clondalkin
- John O'Brien (Louth footballer), Gaelic footballer for Louth
- John O'Brien (soccer), American soccer player
- Jon O'Brien, English footballer
Other sports
- John O'Brien (basketball, born 1888), American basketball referee and executive
- John O'Brien (basketball, born 1916), American professional basketball player in the 1940s
- John O'Brien (boxer), Scottish boxer of the 1960s and '70s
- John O'Brien (cricketer, born 1961), English cricketer
- John O'Brien (Irish cricketer), Irish cricketer
- John O'Brien (hurler), Irish hurler
- John O'Brien (rower), New Zealand representative rower
- John O'Brien (tennis), Australian tennis player and hostage in the 2014 Sydney hostage crisis
- John O'Brien (water polo), Australian Olympic water polo player
- John Ambrose O'Brien, founding owner of the Montreal Canadiens ice hockey team
- John O'Brien (businessman), British businessman
- John O'Brien (rugby union), New Zealand international rugby union player
Other people
- John O'Brien (marine artist), Canadian marine artist
- John O'Brien, the original name of stage actor John T. Raymond
- John O'Brien (poet), Australian priest, poet and author
- John B. O'Brien, American actor and director
- John O'Brien (publisher), Irish American publisher and academic
- John O'Brien (novelist), American author
- John O'Brien (filmmaker), Vermont film director
- John O'Brien (advocate), disability inclusion advocate and writer
- John O'Brien (screenwriter), screenwriter of Fireflies and K-9
- John Roger O'Brien, birth name of Jack O'Brien (jazz pianist)
- Johnny B. O'Brien, one of The 2 Johnnies, Ireland