Thomas Charles O'Brien (June 19, 1887 – November 22, 1951) was an American attorney and politician who served as District Attorney of Suffolk County, Massachusetts and was the United States vice-presidential nominee for the Union Party in the 1936 United States presidential election.

In 1919 he was appointed Boston's commissioner of penal institutions by Mayor Andrew James Peters.

In 1922 he was appointed District Attorney of Suffolk County to fill the unexpired term of Joseph C.

He finished 5th in the 10 candidate field behind Malcolm Nichols, Theodore A. Glynn, Joseph H. O'Neil, and Daniel H.

[7] The Union Party's ticket of U.S. Representative William Lemke and O'Brien received 2% of the vote in the presidential election.