Shirō Hamaguchi is a Japanese anime composer, arranger and orchestrator. He is best known for composing music to the anime franchises Girls und Panzer, One Piece, and Oh My Goddess! and arranging/orchestrating music in the Final Fantasy series. He frequently collaborates with fellow composers Kohei Tanaka and Akifumi Tada on anime scores.

One Piece is a Japanese manga series written and illustrated by Eiichiro Oda. It has been serialized in Shueisha's shōnen manga magazine Weekly Shōnen Jump since July 1997, with its individual chapters compiled in 108 tankōbon volumes as of March 2024. The story follows the adventures of Monkey D. Luffy and his crew, the Straw Hat Pirates, where he explores the Grand Line in search of the mythical treasure known as the "One Piece" in order to become the next King of the Pirates.