Andrew McKellar, MBE, FRSC (February 2, 1910 – May 6, 1960) was a Canadian astronomer who first detected the presence of molecular matter in interstellar space, and found the first evidence of the cosmic radiation left over from the Big Bang.
He was born in Vancouver, British Columbia, Canada, to Scottish parents, one of six children of John H. and Mary Littleson McKellar. He studied mathematics and physics at the University of British Columbia, graduating in 1930.