Jason William Grabowski (born May 24, 1976 in New Haven, Connecticut) is a retired Major League Baseball player. Graduated from The Morgan School in Clinton, Connecticut in 1994. In the 2005 offseason, his contract was sold to the Orix Buffaloes of Japan's Pacific League. He was a 2007 non-roster invitee to the Tampa Bay Devil Rays spring training, but did not make the team and was reassigned to the minors.
He once hit two grand slams in one day. The first came off Dan Andros during a game at Burguiere Stadium, the second off Chris Amoroso at Old Saybrook Stadium. As of the end of the 2006 season, Grabowski held the record for the longest home run (483 ft) at Citizens Bank Park, the Phillies home stadium until it was broken that same season by the Phillies' own Ryan Howard when he hit a 496-foot homer to dead center field.