Ryan Castellani (born April 1, 1996 in Philadelphia, PA) is a former  professional baseball pitcher for the Colorado Rockies and Oakland Athletics of Major League Baseball (MLB). Castellani attended Brophy College Preparatory in Phoenix, Arizona. He was drafted by the Colorado Rockies in the second round of the 2014 Major League Baseball Draft and signed.

The Rockies added Ryan to their 40-man roster after the 2018 season. He also made 7 starts with the Salt River Rafters of the Arizona Fall League following the 2018 season. He spent 2019 with the Albuquerque Isotopes, and returned to the Salt River Rafters following 2019. On June 23, 2020, it was announced that he had tested positive for COVID-19. He returned in time for the start of summer camp on July 4. Ryan made his major league debut with the Rockies on August 8, 2020, against the Seattle Mariners, retiring the first 12 batters he faced.

Castellani opened two games for Italy in the World Baseball Classic in March 2023, with two earned runs and three strikeouts over four innings.

(excerpted from Baseball Almanac, BR Bullpen & Wikipedia)