Gabriel Antonio Martínez Díaz (March 18, 1940 – August 24, 1991) was a Cuban-born Major League Baseball shortstop who played in parts of four seasons for the Cleveland Indians (1963–66), appearing in 73 career games.

The native of Perico threw and batted right-handed, stood 5 feet 10 inches (1.78 m) and weighed 165 pounds (75 kg).

Martínez' professional career began at the Class C level in 1960, but by his third pro season he was an All-Star shortstop in Triple-A, winning the 1962 Most Valuable Player Award in the International League at age 22 as a member of the pennant-winning Jacksonville Suns.

Finally, on May 26, Cleveland optioned Martínez back to Jacksonville and acquired his replacement at shortstop, Dick Howser, in a trade with the Kansas City Athletics.

He was traded along with Jerry Buchek and Art Mahaffey from the St. Louis Cardinals to the New York Mets for Ed Bressoud, Danny Napoleon and cash on April 1, 1967.