Gaku Oshida is a Japanese actor and dancer who portrayed Geiz Myokoin/Kamen Rider Geiz in "Kamen Rider Zi-O". Until March 31, 2021, Oshida was affiliated with Ever Green Entertainment.

In November of 2016, Oshida was the winner of the 29th Junon Super Boy Contest and attended the contest alongside contestants Hiroki Iijima and Ryutaro Okada. He made his first drama appearance in a live-action adaptation of the manga series "Inside Mari". In mid-2018, he was cast as Geiz Myokoin in "Kamen Rider Zi-O".