Gakuto Oshiro (大城ガクト, Ōshiro Gakuto, born July 4, 1973), better known by his mononymous stage name Gackt (stylized in all caps), is a Japanese singer-songwriter, musician, record producer and actor.

Born in Okinawa, Japan, to a Ryukyuan family, Gackt learned the piano at a young age and was raised on classical music and enka before becoming interested in rock music while attending high school. He has been active since 1993, first as the frontman of the short-lived independent band Cains:Feel, and then from 1995 the now-defunct visual kei rock band Malice Mizer. Gackt started his solo career in 1999 with debut mini-album Mizérable and first full-length album Mars (2000). He has released nine studio albums and, with forty-eight singles released, holds the male soloist record for most top ten consecutive singles in Japanese music history. They are mostly conceived around two conceptual stories "Moon Saga" (Moon, Crescent, Diabolos, Last Moon) and "Requiem et Reminiscence" (Rebirth, Re:Born) which are performed live in uniquely elaborate concerts. His single "Returner (Yami no Shūen)" (2007), is his first and only single to reach the number one spot on the Oricon charts. As a solo artist, Gackt has sold over 10 million records. In 2007 became a founding member of S.K.I.N., a Japanese visual kei rock supergroup.

Besides being established in the modern entertainment industry and considered a pop icon, Gackt's music has been used as theme songs for video games (Dirge of Cerberus: Final Fantasy VII), video game films (Dragon Age: Dawn of the Seeker), anime series/films (New Fist of the North Star, Mobile Suit Zeta Gundam, Texhnolyze and Trickster) and television series (Kamen Rider Decade). In addition to his music career, Gackt has voice acted (including characters inspired by him in video games like in Bujingai and Genesis Rhapsodos in Crisis Core: Final Fantasy VII), and live acted in a few films, including a film he wrote, Moon Child, his international debut Bunraku, Japan Academy award nomination performance for Best Actor in Fly Me to the Saitama, and TV series most notably as Uesugi Kenshin in the NHK drama Fūrin Kazan. He also performed live in theatre stage plays, Nemuri Kyoshiro Buraihikae and a duology he has written, composed, and directed Moon Saga: Mysteries of Yoshitsune I & II. He also provided the voice samples for Internet Co., Ltd.'s first Vocaloid, Gackpoid.