Andy Murray says he feels “very proud” to become the first British singles player to be world number one since computerised rankings began in 1973.
The Scot, 29, needed to reach the final of the Paris Masters to replace Novak Djokovic – and did so when Milos Raonic pulled out before their semi-final.
Murray won Wimbledon and Olympic gold in 2016, reached 11 finals in 12 events and won a personal record 73 matches.
“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, who has won three Grand Slam titles, two Olympic gold medals and helped Britain win the Davis Cup in 2015, will be officially confirmed as world number one when the revised rankings are released on Monday.
Novak Djokovic had topped the rankings for 122 weeks, and completed his career Grand Slam by beating Murray in the French Open final in June, his 12th major title.
Djokovic also won this year’s Australian Open, and Murray said: “The year that Novak has had, barring the last six weeks or so, has been incredible.
“The year I’ve had to have to barely get there has been unbelievably difficult. I’ve had to work extremely hard.”
Roger Federer (17) and Rafael Nadal (14) have won a combined 31 Grand Slam titles, many coinciding with Murray’s rise through the rankings.
He will play John Isner in Sunday’s Paris Masters final, after Raonic pulled out with an injury to his right quad. Isner beat Marin Cilic 6-4 6-3 in the semi-finals.