Viktor Amazaspovich Ambartsumian was an Armenian astronomer. His surname is sometimes given as Ambarzumian or Ambarzumyan or Ambarzumjan, and his first name is sometimes given as Victor. His middle name is sometimes given as just Amazasp (Hamazasp, a well known Armenian name).

He was born in Tbilisi, Georgia. After graduating in Leningrad he studied with Aristarkh Belopolsky at Pulkovo Observatory from 1928 to 1931.

Longtime president of the Armenian Academy of Sciences, founder and director of the Byurakan Astrophysical Observatory (BAO) in 1946. He was one of the pioneers of theoretical astrophysics. He worked on the cosmogony of stars and galaxies, stellar dynamics, and gaseous nebulas. In 1947 he discovered stellar associations.

Byurakan Observatory is located on the southern slopes of Mt. Aragats. World renowned by astronomers, it was headed by Viktor Hambartsumian who was also the President of the International Astronomical Union (IAU). During his time at the observatory, Viktor developed theories of young star clusters and computing the mass ejected from nova stars.

He won the Bruce Medal in 1960, and also the Gold Medal of the Royal Astronomical Society in that same year. He won the Lomonosov Gold Medal in 1971.

The asteroid 1905 Ambartsumian is named after him.

He had four children: Ruben, Rafael, Karine, Heghine.