Sinner, 21, won the Toronto title 6-4, 6-1 in the final against Australian Alex de Minaur, who moves up six places to 12th.
Spain’s Carlos Alcaraz, 20, the reigning Wimbledon and US Open champion, holds the number one ranking ahead of Serb Novak Djokovic and Russian Daniil Medvedev.
Denmark’s Holger Rune moves up to fifth with Norway’s Casper Ruud slipping two places to seventh.