Sadao Watanabe (渡辺 貞夫, Watanabe Sadao, born 1 February 1933) is a Japanese jazz musician who plays alto saxophone and sopranino saxophone. He is known for his bossa nova recordings, although his work encompasses many styles, with collaborations from musicians all over the world.

In 1969, Watanabe began working part time as a radio broadcaster, promoting jazz across Japan. From 1972, his programme My Dear Life ran for 20 years. He continued to perform internationally, including performances at Montreux Jazz Festival and Newport Jazz Festival. In 1970, he released his album Round Trip, featuring Chick Corea, Jack DeJohnette, and Miroslav Vitouš. Watanabe continued performing and recording throughout the 1970s and 1980s, amassing a catalogue of more than 70 albums as leader.