Serena Williams has been confirmed as the oldest woman to reach world number one at the age of 31 years and 145 days.
Williams replaces Victoria Azarenka in top spot of the WTA rankings.
The 15-time Grand Slam winner last held the position in October 2010 before a serious foot injury.
Williams back at the top
- Williams first became world number one on 8 July, 2002, at the age of 20
- It is the sixth time in her career that she has earned the top ranking
- Williams missed almost a year due to injury and a life-threatening pulmonary embolism in 2011, slipping as low as 175th in the rankings
- She won Wimbledon, Olympic gold, the US Open and the WTA Championships when she returned in 2012
- Williams has won 60 of her last 63 matches
Williams replaces fellow American Chris Evert as the oldest woman to be number one - Evert held the top ranking in 1985 just before turning 31.
British men's number one Andy Murray
remains the world number three
Britain's top female player Heather Watson stays at number 41 while Laura Robson rises two places to 43, equalling her highest ranking to date.
Williams missed almost a year on the tour after winning Wimbledon in 2010, when she
cut her feet on broken glass
and required two operations on her right foot, before suffering blood clots in her lungs.
She slipped as low as 175th in the rankings but in 2012, her first full season back on the tour, she won Wimbledon, Olympic singles gold, the US Open and the WTA Championships.
And she confirmed her return to top spot by reaching the semi-finals of the Qatar Open. Despite
losing in the final to Azarenka
, Williams had amassed enough rankings points to overtake the Belarusian.
Oldest WTA world number ones
- Serena Williams
- 31 years, 4 months, 24 days
- Chris Evert
- 30 years, 11 months, 3 days (Nov 24, 1985)
- Martina Navratilova
- 30 years, 9 months, 29 days (Aug 16, 1987)
- Lindsay Davenport
- 29 years, 7 months, 8 days (Jan 29, 2006)
- Serena Williams
- 29 years, 0 months, 14 days (Oct 10, 2010)
- Steffi Graf
- 27 years, 9 months, 16 days (Mar 30, 1997)
Azarenka ended a run of nine consecutive defeats against Williams with a 7-6 (8-6) 2-6 6-3 victory to take the title.
This week both players are in Dubai for the Duty Free Championships and are seeded to meet again in Saturday's final.
Williams's coach Patrick Mouratoglou, who said "it was a bit shocking" that Williams had not become world number one sooner given her achievements in 2012, believes she can go on to match legends Martina Navratilova and Chris Evert, who both won 18 Grand Slam singles titles.
"That's her main motivation and I think she will keep that," Mouratoglou said.
"I don't think it's hard, but she needs a few things. She needs to stay healthy first, because at 31 that's something really difficult.
"So the main thing is staying fit and the motivation. If she does those two she'll keep on improving - if she wants to. If she achieves both, I think she can still win more Slams. Why not 18? She's not that far from 18."
- Heather Watson 41, Laura Robson 43, Johanna Konta 153, Anne Keothavong 185, Elena Baltacha 191
- Andy Murray 3, James Ward 205, Jamie Baker 206, Josh Goodall 261