Atle Selberg (14th June, 1917 - 6th August, 2007) was a Norwegian mathematician. He was born in Langesund, Norway, and studied mathematics at the University of Oslo, where he 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 gave an independent proof. He immigrated to the United States and works at the Institute for Advanced Study in Princeton where he died in 2007.
He introduced spectral theory into number theory and developed the Selberg trace formula.