Masakatsu Morita (森田 必勝 Morita Masakatsu, Yokkaichi, 25 July 1945 - Tokyo, 25 November 1970) was the Tatenokai member who attempted to commit seppuku with Yukio Mishima at the Ichigaya Camp.
He was the youngest child of a headmaster. Losing both parents at the age of two, he was cared for by his brother Osamu and educated at a Catholic school. He entered Waseda University in 1966 but was dismayed by the presence of the Zengakuren and became heavily involved in the small right-wing faction at the university. He came into Mishima's orbit in 1967, and joined the Tatenokai at its establishment the next year.
Mishima approached several members one at a time in April and May 1970. The inner circle then consisted of Mishima, Morita, Ogawa and "Chibi" Koga. No clear plan was developed until late June. Shortly afterwards he went on holiday to Shimoda and paid for the others to go to Hokkaidō, where they recruited "Furu" Koga, whom Mishima met on 9 September in Tokyo.
All four followers were expecting to commit suicide, and were indignant when, in November, Mishima ruled that only he and Morita were to die. On the 21st and 22nd, supplies were bought, and Morita asked "Furu" Koga to stand in for him if he should fail to behead Mishima properly. The next two days were spent in rehearsal. In the end, Koga beheaded both Mishima and Morita.