Thomas James O’Brien (July 30, 1842 – May 19, 1933) was a politician and diplomat from the U.S. state of Michigan.
O'Brien was born in Jackson, Michigan, on July 30, 1842, the son of Timothy O'Brien and Elizabeth Lander O'Brien. On September 4, 1873, he married Delia Howard (July 14, 1848 - January 22, 1926).
O'Brien was a lawyer by profession and a Republican politician. In 1883 he was an unsuccessful candidate for the office of Justice of the Michigan Supreme Court. In 1896 and 1904 he was a delegate to the Republican National Convention from Michigan.