Kim Clijsters of Belgium reclaimed the No. 1 ranking by defeating Jelena Dokic of Australia 6-3, 6-0 on Friday to reach the semifinals of the Open Gaz de France.
Clijsters will replace Caroline Wozniacki of Denmark at the top when the new rankings are released on Monday.
''I'm very happy to be number one again,'' Clijsters said after being presented with a special trophy and a giant No. 1 made from flowers.
The 27-year-old Clijsters has held the top ranking three times before, but not since 2006. She retired in May 2007 before marrying U.S. basketball player Brian Lynch and giving birth to a daughter, Jada, in February 2008.
Since making her competitive return in August 2009, Clijsters has won three Grand Slam titles, and is the current champion at the U.S. and Australian Opens. Wozniacki is still chasing her first major.
''I'm older, a little more experienced,'' Clijsters said. ''I'm able to enjoy all the things that are happening now in a different way. I'm able to share it with a bigger group and with my team. That's what I enjoy the most about this second career.''
The 256-week stretch between Clijsters' last spell at No. 1 and the current one is the second longest in ATP or WTA history, beaten only by Serena Williams (265 weeks).
As the speakers of the stadium blasted Tina Turner's 'Simply The Best,' the WTA put on a special presentation to celebrate Clijsters' achievement.
''It's weird because you're in the middle of a tournament,'' Clijsters said. ''You're doing a speech, you're getting a trophy and flowers, so it's a little bit weird but exciting as well.''
Before leaving the court, Clijsters signed autographs and gave away towels, and posed for photos for spectators.
Clijsters' win came after she reeled off 12 games in a row against Dokic, having trailed 3-0 in the first set.
''She came out strong and served well and was returning well,'' Clijsters said. ''I kind of just got overpowered by the way she was playing. But I knew that if I could win a couple of rallies, I would be able to turn things around.''
Clijsters will face Kaia Kanepi of Estonia or Slovakia's Dominika Cibulkova in the semifinals in Paris.
Also on Friday, Bethanie Mattek-Sands of the United States upset sixth-seeded German Andrea Petkovic 7-6 (4), 2-6, 6-3 and will meet Petra Kvitova in the last four after the Czech player edged Belgium's Yanina Wickmayer 5-7, 6-3, 7-6 (3).
Mattek-Sands said Clijsters deserved to hold the No. 1 ranking.
''To have Kim come back, win two Slams in a row now, I think she's definitely deserving of it,'' Mattek-Sands said.
''Nothing against Caroline (Wozniacki), she's had a very consistent year last year. That's deserving as well.''
Amelie Mauresmo, the tournament's co-director and a former top-ranked player, praised Clijsters' performance.
''What she has achieved is quite extraordinary,'' Mauresmo said. ''It's a bit surprising because she suffered a lot injuries in her first career. But she stopped at a young age, so she's physically able to still be very competitive.
''That she becomes again the No. 1 is quite logical. Serena (Williams) is not able to be fit. Wozniacki is very consistent but so far she hasn't peaked yet.''
