Peter Sarnak is South African/American mathematician who, with Alex Lubotzky and Ralph Phillips, introduced Ramanujan graphs which have led to advances in theoretical computer science, differential geometry, algebraic groups and finite groups. He has received many major awards including the Pólya Prize, the Ostrowski Prize, the Levi L Conant Prize, the Frank Nelson Cole Prize, the Paul R Halmos-Lester R Ford Prize and the Wolf Prize.