Robert Gordon Martyn (August 15, 1930 – December 2, 2015) was an American right fielder in Major League Baseball who played for the Kansas City Athletics in parts of three seasons spanning 1957–1959.

In the 1956 American Association All-Star Game, he hit two home runs and earned Most Valuable Player honors.

On June 15, 1957, the Yankees traded Martyn along Woodie Held, Billy Martin and Ralph Terry to the Athletics in the same transaction that brought Ryne Duren, Jim Pisoni and Harry Simpson to New York.

Just three days after the trade, Martyn made his big league debut facing the Washington Senators.

The following year, he appeared in 95 games and batted .261 (59-for-226) with two homers and 23 RBI, ending sixth in the American League with seven triples and ninth with five intentional walks.

On April 12, 1959, he was traded back to the Yankees along with Mike Baxes in exchange for Tom Carroll and Russ Snyder.