Murray needed only to reach the final in Paris after current number one Novak Djokovic lost to Marin Cilic in Friday’s quarter-final.
Canadian Raonic, however, announced before Saturday’s match that he was injured.
Murray will be the first British singles player to hold top spot since computerised rankings began in 1973.
On the other hand, John Isner has cruised to a straight-sets victory over Marin Cilic to meet Murray in the finals.
This means that Isner would finish the year as the number one American for the fifth consecutive year.