Mario Valenzuela Osuna (born March 10, 1977 in Isla San Marcos, Baja California Sur, México) is a professional baseball outfielder for the Guerreros de Oaxaca.
Valenzuela currently plays for the Diablos Rojos del México of the summer Mexican Baseball League and the Algodoneros de Guasave of the Mexican Pacific League. He formerly played for the Chicago White Sox minor league affiliates, beginning in 1996 at the age of 19 by playing in the Rookie League and eventually achieving Triple-A level in 2004.
In 2006, Valenzuela played for Team Mexico in the World Baseball Classic, finishing the tournament batting .250 with a home run and one run batted in.
For the 2009 World Baseball Classic edition, he joined Team Mexico as a replacement player for the injured Erubiel Durazo, going hitless in four at bats.