Koichi Sugiyama (すぎやまこういち, Sugiyama Kōichi, April 11, 1931 – September 30, 2021) was a Japanese composer, conductor, and orchestrator. He was best known for composing for the Dragon Quest franchise, along with several other video games, anime, film, television shows, and pop songs. Classically trained, Sugiyama was considered a major inspiration for other Japanese game music composers and was active from the 1960s until his death from septic shock in 2021.

Sugiyama was also a council member of the Japanese Society for Rights of Authors, Composers, and Publishers (JASRAC), board member of the Japan Institute for National Fundamentals, and honorary chairman of the Japanese Backgammon Society. Prior to his death, the Japanese government honored him with Order of the Rising Sun and named him a Person of Cultural Merit. Sugiyama was also active in politics and activism, promoting ideas such as Japanese nationalism while denying Japanese war crimes.