Murray, 29, replaces Novak Djokovic at the top of the rankings on Monday and claimed his eighth title of a remarkable season
Andy Murray celebrated his new world number one ranking with a first Paris Masters title on Sunday after defeating American John Isner 6-3, 6-7 (4/7), 6-4 in the final.
Murray, 29, replaces Novak Djokovic at the top of the rankings on Monday and claimed his eighth title of a remarkable season after extending his winning run to 19 matches.
"This has been an incredible journey for me to get to the top of the rankings," said Murray, who will move 405 points above long-time rival Djokovic.
"Sometimes after you achieve something big or something that you maybe didn't expect, it can be quite easy to have a letdown and feel a little bit flat.
"I felt really nervous before the match today, and I was happy about that."
He added: "It would be nice to finish the year number one, but I'm happy that I managed to get there."
It is the Briton's fourth title in succession after wins in Beijing, Shanghai and Vienna and his 14th career Masters 1000 triumph.
Murray will next look to end Djokovic's four-year dominance at the November 13-20 Tour Finals in London.
For Isner, who finishes the season without a title for the first time since 2009, it was his third appearance in a Masters final after finishing runner-up at Indian Wells in 2012 and Cincinnati in 2013.
"I have to congratulate Andy, first for the title, and then for getting to number one in the world. That's an incredible achievement, you absolutely deserve it," said Isner.
"It's a good week for me. It's definitely disappointing. I certainly wasn't happy to be there today, getting to the finals, I wasn't happy about that.
"I wanted to win, and I expected to win. I just fell a little bit short."
Murray entered his Tour-leading 12th final of the year having won all seven previous meetings with Isner, including straight-sets wins at Roland Garros in May and last week in Vienna.
The towering American had dropped serve just three times en route to the final but netted a routine volley to hand Murray break point in the fifth game.
His backhand then sailed long the following rally as Murray forged ahead, saving two break points on his ensuing service game before claiming the opening set.
Murray fought off four break points after rebounding from 0-40 at 3-4 in the second set, but Isner prevailed in the tie-break after a costly double fault from the second seed.
The Scot was then frustrated as he twice failed to convert break points during Isner's first two service games in the deciding set.
But Murray held firm and was rewarded when Isner faltered as he tried to stay in the match serving at 4-5 down.
The world number 27 dug himself out of a hole after trailing 0-30, but a backhand volley into the net presented Murray with match point.
Isner approached the net once more and Murray's return was again too hot to handle, leaving the new number one to hoist aloft the trophy.