Mario Ayelar Valdez (born November 19, 1974) is a Mexican former professional baseball first baseman.

He played during three Major League Baseball (MLB) seasons for the Chicago White Sox and Oakland Athletics.

He enrolled at Miami Senior High School for his final year of high school and earned a college baseball scholarship to Miami Dade College where he planned to study international business before returning to Mexico.

His last MLB-affiliated season was in 2003, when he played for the San Diego Padres' Triple-A unit, the Portland Beavers.

Valdez played with Mexican team Tomateros de Culiacan in winter ball in La Liga Mexicana del Pacifico.