Giomar Antonio Guevara Díaz (born October 23, 1972) is a Venezuelan former professional baseball infielder. He played parts of three seasons in Major League Baseball, from 1997 through 1999, for the Seattle Mariners. Listed at 5' 8" (1.73 m), 150 lb. (68 k), Guevara was a switch-hitter and threw right-handed. He was born in Guarenas, Miranda.

Guevara [gay-vah'-rah] played for Seattle in parts of three seasons as a backup for shortstop Alex Rodriguez. He also spent 10 campaigns in the Minor leagues with the Detroit Tigers, Oakland Athletics and Mariners organizations.

In between, Guevara played winter ball with the Leones del Caracas and Tigres de Aragua clubs of the Venezuelan League between the 1993–2001 seasons.