Thomas H. O'Brien (June 22, 1860 – April 21, 1921) was an infielder in Major League Baseball who played for five clubs in parts of six seasons between 1882 and 1890. O'Brien batted and threw right-handed. He was born in Salem, Massachusetts. In 270 games, O'Brien was a .231 hitter (257-for-1111), including 74 extra-base hits and 61 RBI. O'Brien died in Worcester, Massachusetts, at the age of 60.