Tadao Sawai (沢井忠夫, Sawai Tadao, 1938 – April 1, 1997) was a Japanese koto player and composer. He was renowned all over Japan for his skill at the koto and also received acclaim for his compositions. He was married to Kazue Sawai, also a koto player, and their son Hikaru Sawai is also a musician.

Born in Aichi Prefecture, Sawai graduated from the Tokyo National University of Fine Arts and Music in 1958.

Sawai worked with a number of Western musicians, including Wadada Leo Smith and also released a CD of himself playing Jazzy Bach on the Koto.

Sawai also invented a Koto of his own also called as the Tadao koto which also creates good sounds.