Atle Selberg is a Norwegian mathematician. He was born in Langesund, Norway, on 14th June, 1917. He studied mathematics at the University of Oslo and obtained his Ph.D in 1943. 
In 1948 he provided a long-awaited elementary proof of the prime number theorem, around the same time that Paul Erdős provided an independent proof. He immigrated to the United States and works at the Institute for Advanced Study in Princeton.
He introduced spectral theory into number theory and developed the Selberg trace formula.