Saegusa Shigeaki is a Japanese composer.

Saegusa is best known for his opera version Chuushingura of the well-known kabuki epic of the Forty-seven Ronin/Chuushingura with a libretto by the novelist Shimada Masahiko. Written over a period of 10 years, the opera was most recently performed at the New National Theatre, Tokyo in 2002. His newest opera, Jr. Butterfly is a sequel of Giacomo Puccini's Madama Butterfly.

He has also written the background music for anime, the foremost of which being Mobile Suit Zeta Gundam. Other anime he has written for are Mobile Suit Gundam ZZ, Mobile Suit Gundam: Char's Counterattack, Catnapped! The Movie, and Mother: Saigo no Shoujo Eve.