Harold Winthrop Martin (September 23, 1887 – April 14, 1935) was an American Major League Baseball pitcher.

[1] In 1911, he joined the Athletics after finishing his college semester in June and then returned to college after the end of the World Series, which the Athletics won although Martin did not pitch in the series.

[1] The 1912 Reach Guide described him as a "clever young pitcher" and said that the Athletics were "fortunate" in his "gradual development" in their pursuit of the 1911 league championship.

[3] Martin played semi-pro baseball prior to 1911 for a team in Rockport, Massachusetts, where he was a teammate of future Athletics teammate Stuffy McInnis.

This biographical article relating to an American baseball pitcher born in the 1880s is a stub.