Masutatsu Ōyama, born Choi Yeong-eui (Hangul: 최영의 Hanja: 崔永宜), more commonly known as Mas Oyama, was a karate master who founded Kyokushin Karate, considered the first and most influential style of full contact karate. A Zainichi Korean, he spent most of his life living in Japan and acquired Japanese citizenship in 1968.