Thomas O'Brien
Thomas O’Brien, Tom O’Brien, or Tommy O'Brien may refer to:
Politicians
- Thomas C. O'Brien, American politician and lawyer
- Thomas J. O'Brien (Illinois politician), Illinois politician
- Thomas J. O'Brien (Massachusetts politician), Massachusetts state representative
- Thomas J. O'Brien (Michigan politician), Michigan politician and U.S. ambassador
- Thomas P. O'Brien, former United States attorney for the Central District of California
- Sir Tom O'Brien (trade unionist), British trade unionist and member of parliament
Sportspeople
- Thomas O'Brien (footballer), Scottish footballer
- Tom O'Brien (American football), former American college football coach at NC State
- Tom O'Brien (footballer, born 1889), Australian rules footballer for University
- Tom O'Brien (footballer, born 1904), Australian rules footballer for Melbourne
- Tom O'Brien (jockey), Irish jockey
- Tom O'Brien (outfielder), Major League Baseball outfielder/infielder
- Tom O'Brien (second baseman), baseball player
- Tommy O'Brien (baseball), Major League Baseball outfielder
- Tommy O'Brien (rugby union), Irish rugby union player
- Tommy O'Brien (basketball), American basketball player
Others
- Thomas O'Brien (bishop), Church of Ireland bishop of Ossory, Ferns, and Leighlin
- Thomas O'Brien (interior designer), American designer
- Thomas D. O'Brien, co-founder of William Mitchell College of Law
- Thomas J. O'Brien (bishop), bishop of Phoenix, 1982–2003
- Thomas W. O'Brien, Canadian entrepreneur and pioneer
- Thomas Alexander O'Brien, New Zealand cinema owner and entrepreneur
- Thomas Enraght O'Brien, lord lieutenant of Limerick
- Tom O'Brien (actor, born 1890), American film actor
- Tom O'Brien (actor), American film actor
- Tom O'Brien (swindler), American confidence man and swindler