Gregorio "Joy" Dionisio (born April 4) is a retired Filipino professional basketball player.

He was a guard and forward for the Adamson Falcons in the University Athletic Association of the Philippines (UAAP).

After playing his last UAAP year, Dionisio reunited with his fellow Adamson star Ompong Segura when they played in the Asian Basketball Confederation (ABC) and won gold for the Philippine national team in 1972.

[2][3] His other teammates included Atoy Co, Ramon Fernandez, Philip Cezar, and Rino Salazar.

[4][5][6][7] At PBA's inaugural season, Dionisio hit the first basket on April 9, 1975 at the Araneta Coliseum and went on to become an eight-time champion in the pro league.