Mstislav Vsevolodovich Keldysh (Russian: Мстисла́в Все́володович Ке́лдыш; 10 February [O.S. 28 January] 1911 – 24 June 1978) was a Soviet scientist in the field of mathematics and mechanics, academician of the USSR Academy of Sciences (1946), President of the USSR Academy of Sciences (1961–1975), three times Hero of Socialist Labor (1956, 1961, 1971), fellow of the Royal Society of Edinburgh (1968). He was one of the key figures behind Soviet space program.