Andy Murray has gone 24 matches without defeat
Andy Murray beat five-time champion Novak Djokovic to win his first ATP World Tour Finals title and end 2016 as the world number one.
With the top ranking on the line, Murray won the final 6-3 6-4 at London's O2 Arena.
"I'm very happy to win and to be world number one is very special," said the Scot. "It's very special playing against Novak in a match like this."
Murray extended his winning run to 24 matches, the best run in his career.
The victory also ends Djokovic's four-year run of success at the tournament.
A capacity crowd of 17,000 packed into the O2 Arena to witness the match, and it was Murray who rose to the occasion.
"Andy is definitely number one in the world," said Djokovic. "He deserved to win. He is the best player."
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How the world reacted
Andy's brother Jamie has finished the year world number one in doubles
Seven-time Grand Slam champion had praise for both players
British women's number one Johanna Konta is 10th in the world
Harry Potter author JK Rowling cheered Murray on...
... as did Match of the Day presenter Gary Lineker
Golfer Justin Rose won Olympic gold in Rio, as did Murray
The Scottish First Minister was thrilled by Murray's win
Perhaps last word should go to mum...
Andy and Jamie Murray's mum, Judy, tweeted shortly after Sunday's win