Santiago Casilla (born June 25, 1980, in San Cristóbal, Dominican Republic) is a right-handed Major League Baseball relief pitcher for the Oakland Athletics.

Casilla was signed by the Athletics on January 31, 2000, as an amateur free agent.

Casilla pitched from 2000 to 2005 under the name of Jairo Garcia. In 2006, he revealed his real name to be Santiago Casilla during spring training. He had used false documents when he first signed a contract with the Athletics in 2000.