He beat American John Isner 6-3 6-7 (4-7) 6-4 to secure his sixth ATP title of a memorable 2016.
On Monday he will be officially confirmed as Britain’s first singles number one since computerised rankings were introduced in 1973.
His rise to the top of the world rankings was confirmed on Saturday by Milos Raonic’s withdrawal from Saturday’s semi-final with a thigh injury.
Murray’s next stop is the World Tour Finals and will be hoping Novak Djokovic fails to win every match which would enable him t reclaim the position he held for 122 weeks.
“I never thought I’d be number one in the world,” he told BBC Sport.
“It’s been many years of work to get here. It’s been such a difficult thing to do because of how good the guys around me have been.”
Murray’s opportunity to take the number one position followed Novak Djokovic’s shock defeat to Marin Cilic at the Paris tournament.
Djokovic needed to reach the final to hold on to continue his reign but lost 6-4 7-6 (7-2) to in his quarter-final tie.
Djokovic’s defeat was all the more surprising as Cilic had lost all 14 of their previous meetings.
Murray is the second-oldest player to debut at number one, after the 30-year-old John Newcombe in 1974.
It is also a record for the most time before stepping up from number 2 which he first reached in 2009.
Horse racing: Jockey Freddy Tylicki has been left paralysed from the waist down following a fall in a four-horse collision at Kempton on Monday.
Tylicki suffered a spinal injury after being unseated from Nellie Dean which appeared to clip heels with leader and eventual winner Madame Butterfly, causing a melee on the home turn.
Champion jockey Jim Crowley suffered a broken nose while Steve Drowne and Ted Durcan were unseated. The horses were not injured.
Tylicki is being treated at St George’s Hospital in Tooting, south London. He has movement in the upper half of his body none below the waist.
Lisa Hancock of the Injured Jockeys’ Fund said: “Freddy remains in intensive care and is not receiving any visitors for the foreseeable future.
“His family would like to thank the St George’s staff for the care he has received. As this is a very difficult time for Freddy and his family, they would like to thank everyone for their good wishes, and for continuing to respect their privacy.”