John O'Brien may refer to:
Public officials American John O'Brien (Ohio politician) (1932–1985), 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) (c. 1850–1927), Secretary of State of New York, 1903–1906 John F. O'Brien (judge) (1874–1939), 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) (1919–2001), investigated the assassination of President John F. Kennedy John J. O'Brien (commissioner), former commissioner of the Massachusetts Probation Service John P. O'Brien (1873–1951), 98th mayor of New York City John L. O'Brien (1911–2007), American politician in the Washington State House of Representatives
Irish John O'Brien (bishop) (died 1767), Irish Bishop of Cork and Cloyne John O'Brien (Irish politician) (1794–1855), MP for Limerick City in the UK Parliament 1841–1852 John O'Brien (priest) (1931–2008), Irish Roman Catholic priest and musician John Thomond O'Brien (1786–1861), 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) (died 1982), far right figure, onetime leader of the British National Front Sir Terence O'Brien (colonial administrator) (John Terence Nicholls O'Brien, 1830–1904), British surveyor, engineer and colonial governor
Canadian John O'Brien (admiral) (1918–1996), commander of the Royal Canadian Navy John O'Brien (Canadian politician) (1847–1917), merchant and member of the Legislative Assembly of New Brunswick
New Zealand John O'Brien (New Zealand politician) (1925–1990), New Zealand political candidate and party leader
Australian John O'Brien (Australian politician) (1866–1932), Member of the Queensland Legislative Assembly John O'Brien (Australian Army officer) (1908–1980), Australian major general and Mayor of Woollahra
Sportspeople Baseball John O'Brien (outfielder) (1851–1914), baseball outfielder John O'Brien (second baseman) (1866–1913), baseball infielder Johnny O'Brien (1930–2025), 1950s baseball second baseman Cinders O'Brien (John F. O'Brien, 1867–1892), baseball pitcher
Footballers John O'Brien (Dublin footballer), senior inter-county Gaelic footballer for Dublin and Round Towers, Clondalkin John O'Brien (Louth footballer) (born 1985), Gaelic footballer for Louth John O'Brien (soccer) (born 1977), American soccer player Jon O'Brien (born 1961), English footballer
Other sports John O'Brien (basketball, born 1888) (1888–1967), American basketball referee and executive John O'Brien (basketball, born 1916) (1916–1994), American professional basketball player in the 1940s John O'Brien (boxer) (1937–1979), Scottish boxer of the 1960s and '70s John O'Brien (cricketer, born 1961), English cricketer John O'Brien (Irish cricketer) (1866–1920), Irish cricketer John O'Brien (hurler) (born 1982), Irish hurler John O'Brien (rower) (1927–1995), New Zealand representative rower John O'Brien (tennis) (born 1932), Australian tennis player and hostage in the 2014 Sydney hostage crisis John O'Brien (water polo) (1931–2020), Australian Olympic water polo player John Ambrose O'Brien (1885–1968), 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) (1831–1891), Canadian marine artist John O'Brien, the original name of stage actor John T. Raymond (1836–1887) John O'Brien (poet) (1878–1952), Australian priest, poet and author John B. O'Brien (1884–1936), American actor and director John O'Brien (publisher), Irish American publisher and academic John O'Brien (novelist) (1960–1994), American author John O'Brien (filmmaker) (born 1962), 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 (1903–1982), birth name of Jack O'Brien (jazz pianist) Johnny B. O'Brien, one of The 2 Johnnies, Ireland
See also Jack O'Brien (disambiguation) Sean O'Brien (disambiguation)