Mahlon R. Pitney IV (February 5, 1858 – December 9, 1924) was an American lawyer, jurist, and politician who served in the U.S. House of Representatives for two terms from 1895 to 1899.

He attended the College of New Jersey (now Princeton University) where he was a classmate of Woodrow Wilson and served as manager of the campus baseball team.

He defeated one-term incumbent Johnston Cornish for the seat from New Jersey's 4th congressional district, and was reelected to a second term two years later.

Pitney served as chairman of the 1895 state Republican convention and pushed for the nomination of John W. Griggs as party gubernatorial candidate.

In order to further improve his local standing, he resigned from the House prior to the end of his second term and ran for election to the New Jersey Senate; Pitney was victorious in this 1898 race.

Pitney was nominated by President William Howard Taft on February 19, 1912, to be an associate justice of the Supreme Court of the United States,[5] to succeed John Marshall Harlan.

Although distrustful of unions, Pitney also feared the rampant expansion of business and supported a broader use of the Sherman Antitrust Act.