Tadao Tannaka (?? ??, Tannaka Tadao, December 27, 1908 – October 25, 1986) was a Japanese mathematician.
He is best known for developing the theory of Tannaka–Krein duality, which generalizes Pontryagin duality to noncommutative compact groups.Tannaka was born in Matsuyama, Ehime Prefecture.
After receiving a Bachelor of Science in mathematics from Tohoku Imperial University, he was appointed a lecturer in the university in 1934 and was promoted to a full professor in 1945.