Masao Kotani (小谷 正雄, Kotani Masao, January 14, 1906 – June 6, 1993) was a Japanese theoretical physicist, known for molecular physics and biophysics.Kotani was born in Kyoto and spent his primary and middle school days in Osaka. He moved to Tokyo to enter the First Higher School and then the Imperial University of Tokyo. In 1929, he received his BSc degree in physics and was appointed as a lecturer at the faculty of engineering in the Imperial University of Tokyo.