Samuel Blair Mertes (August 6, 1872 – March 11, 1945) was an American professional baseball player.

Mertes led the National League in doubles and RBIs in 1903 while playing for New York.

Harpo Marx considered Mertes his favorite player, claiming he was the only member of the Giants he could see from his limited view outside the stadium on Coogan's Bluff.

After being traded to St. Louis, he said that he had trouble getting along with his teammates on the New York Giants because he was a Mason and many of them were Irish Catholics.

This biographical article relating to an American baseball outfielder born in the 1870s is a stub.