The 29-year-old Scotsman needed to beat Canadian Milos Raonic in the semi-finals of the Paris Masters to seal the top spot.
But in the end, Murray did not need to hit a single ball as his opponent withdrew before the match began due to a leg injury.
It is the first time that a Briton has reached the number one position, which Serbian Djokovic, 29, held since July 2014.
Murray said: “It feels a little bit strange how it’s happened today and obviously unfortunate that Milos is injured.
“To get to this stage is about 12 months of tournaments. The last few months have been the best of my career and I’m very proud to get to this moment.”
In the last year Murray has won Wimbledon for the second time and retained his Olympic title, lifting a total of seven trophies.
He also made the final of the Australian and French Opens.Since 2004, only four players have held the top spot – Roger Federer, Rafael Nadal, Djokovic and now Murray.
STORY BY SKY SPORTS
