Tadahiro Aizawa (相沢 忠洋, Aizawa Tadahiro, June 21, 1926 – May 22, 1989) was a Japanese archaeologist.

Aizawa, an amateur stone tool collector who had been peddling nattō, discovered a microlith in Iwajuku, Gunma in 1946, which was recognized in 1949 as a Paleolithic site that had previously been thought not to exist in Japan.