Isao Imai (今井 功, Imai Isao, October 7, 1914 – October 24, 2004) was a Japanese theoretical physicist, known for fluid mechanics and mathematical physics.Imai was born on October 7, 1914 in Dairen. A few years later, his family returned to Kobe, where he spent his childhood. He skipped one grade in elementary school and another in middle school, and he entered the First Higher School. He proceeded to the Imperial University of Tokyo, majoring in physics, and graduated at the age of 21.