José Gregorio Castillo Tovar (born January 10, 1996) is a Venezuelan professional baseball pitcher in the Arizona Diamondbacks organization.

He has previously played in Major League Baseball (MLB) for the San Diego Padres.

Castillo signed with the Tampa Bay Rays as an international free agent on July 6, 2012.

[citation needed] The Rays traded Castillo, Wil Myers, Ryan Hanigan and Gerardo Reyes to the San Diego Padres in exchange for René Rivera, Burch Smith and Jake Bauers on December 19, 2014.

He only pitched in 2/3 of an inning for the Padres in 2019, allowing no runs and striking out two, before suffering an injury to his left middle finger and ending the season on the 60-day injured list.

On July 20, 2023, Castillo was designated for assignment following Robert Suárez's activation from the injured list.