Thomas O'Brien
Thomas O'Brien is the name of the following people:
- Thomas O'Brien (Bishop) (1792–1874), Irish clergyman, Bishop of Ossory, Ferns and Leighlin
- Thomas J. O'Brien (diplomat) (1842–1933), American diplomat
- Thomas J. O'Brien (politician) (1878–1964), American politician
- Thomas J. O'Brien (Bishop) (1935–2018), American priest, Bishop of Phoenix
- Thomas Kevin O'Brien (1923-2004), English Catholic bishop