Viktor Amazaspovich Ambartsumian (; 18 September 1908 - August 12, 1996) was an Armenian Soviet astrophysicist. He was one of the founders of theoretical astrophysics. Ambartsumian worked in the field of physics of stars and nebulae and stellar astronomy. He was the founder of the Byurakan Astrophysical Observatory. He was a member of the Russian Academy of Sciences (1953, corresponding member since 1939). He was also a member of the Armenian National Academy of Sciences and its president (1947-1993).