Jack O'Brien may refer to:
Sports Jack O'Brien (American football) (born 1932), American football player Jack O'Brien (catcher) (1860–1910), Major League Baseball player Jack O'Brien (cricketer) (1886–1939), New Zealand cricketer Jack O'Brien (footballer, born 1887) (1887–1959), Australian rules footballer for Essendon and Fitzroy Jack O'Brien (footballer, born 1893) (1893–1934), Australian rules footballer for South Melbourne Jack O'Brien (footballer, born 1898) (1898–1966), Australian rules footballer for Essendon and Footscray Jack O'Brien (footballer, born 1906) (1906–1970), Australian rules footballer for South Melbourne and Hawthorn Jack O'Brien (outfielder) (1873–1933), American baseball player Jack O'Brien (wrestler) (1910–1982), American-born Mexican professional wrestler Jack O'Brien (rugby union), New Zealand international rugby union player Philadelphia Jack O'Brien (1878–1942), American boxer, former light heavyweight boxing champion of the world Young Jack O'Brien (1894–?), lightweight boxer from Pennsylvania
Others Jack O'Brien (director) (born 1939), American theatre director and producer Jack O'Brien (jazz pianist) (1903–1982), big band pianist and songwriter John B. O'Brien (known as Jack, 1884-1936), American actor and film director Jack O'Brien, founder of American website of Cracked.com
See also John O'Brien (disambiguation) Jack O'Brian (1914–2000), journalist