May 14 (Bloomberg) -- Justine Henin, the top-ranked women's tennis player, said she's quitting the sport immediately at age 25 to make ``a new start'' in life.

``It's a relief, a new page is opening up,'' Henin told reporters during a press conference at her tennis academy in Limelette, Belgium. ``I look toward to the future. It's a way of looking at what's essential.''

Henin is retiring after an emotional year, and following her most successful season. She won 10 of the 14 events she entered in 2007, including the French and U.S. opens. Henin skipped the 2007 Australian Open after separating from her husband, Pierre-Yves Hardenne, and patched up her relationship with her estranged father, sister and two brothers. Henin's mother died of cancer when she was 12.

This season, she hasn't been as successful on the court. She withdrew from this week's tournament in Italy complaining of fatigue. Henin lost in the third round of the German Open last week to Dinara Safina, a player who had never won a set against her. She has also struggled with a knee injury.

``It's pretty tough for me in the last few weeks and the last few months,'' said Henin, who has won seven grand Slam titles in her nine years on the WTA Tour. ``The game is tough, you need to be really strong physically and emotionally.''

Henin lost in the quarterfinals of this year's Australian Open to eventual champion Maria Sharapova, who is ranked No. 2 in the world.

Backhand Power

Henin's game was built around her backhand, a one-handed stroke that blistered opponents. She had a reputation for toughness, beating Jennifer Capriati in a 2003 U.S. Open semifinal while battling leg cramps so bad she had to lean on her racket between points and needed intravenous fluids after the match.

She also was occasionally criticized by opponents for a lack of sportsmanship.

Serena Williams, another Grand Slam champion, at the time said she was ``disappointed'' at Henin for not speaking up on a key point during in a quarterfinal at the 2003 French Open, a match the Belgian won. At the 2006 Australian Open, Henin trailed Amelie Mauresmo by a set and a service break in the final when she quit the match, complaining of a stomach ailment. Instead of celebrating her first Grand Slam title on court, Mauresmo was left to go to Henin's chair to see how her opponent was feeling.

Championships Won

Most of the memories around Henin are of championships won, including three straight French Open titles and every Grand Slam except Wimbledon.

``This is a sad day for our sport and for her millions of fans around the world,'' Larry Scott, chief executive of the WTA Tour, said in a statement.

Henin said she had no regrets.

``I want to have my adult life. I want to make choices,'' she said today. ``It's like a new start for me. Most people my age are in school or starting work, and I have the impression I've already lived three lives.''

Her game this year hasn't been on par with other years, said Tracy Austin, the youngest ever U.S. Open champion.

``She has not had the stellar year leading up to the French Open that she had the other years,'' Austin said. ``There is no way that Justine is playing with the amount of confidence, not even close, the way she had when coming into the French before.''

Schedule Makeover

Henin's retirement comes as both the men's and women's tours are restructuring their schedule in answer to player and promoter complaints of too many matches and too much travel.

Martina Navratilova, who won a record 167 career titles, said last week that the 2008 schedule was ``crazy'' and made too many demands on the players.

Standing at 5-foot-5, Henin amassed 41 career titles, including four French Opens, two U.S. Opens and one Australian Open. She is a two-time runner-up on Wimbledon's grass courts.

She also won the season-ending WTA Tour Championships back- to-back and the singles gold medal at the 2004 Athens Olympics.

``Justine was more than a champion, she was a great personality,'' Jacques Rogge, president of the International Olympic Committee and a fellow Belgian, told newswire Belga today. ``She has had to overcome a difficult childhood and had some limitations because of her physique. She will remain an example for youngsters.''

Prize Money

By closing her season with victory at the Tour Championships in November, Henin lifted her prize money for the year to a record $5.4 million, passing the mark of $4.4 million collected by fellow Belgian Kim Clijsters in 2003.

Clijsters quit 12 months ago at age 23 and had her first child in February.

Henin is fifth on the all-time prize money list with $19.4 million and has topped the women's rankings for 61 straight weeks since regaining the No. 1 spot in March last year.

``I took the decision for myself,'' Henin said today. ``It's to breathe again.''

History will remember the Belgian for ``one of the most graceful backhands the sport has ever seen,'' said Scott, of the WTA Tour. The Belgian had ``an ability to overcome any and all obstacles placed in her way on the tennis court and off.''

To contact the reporters for this story: Helene Fouquet in Brussels hfouquet1@bloomberg.net; Danielle Rossingh in London drossingh@bloomberg.net

Last Updated: May 14, 2008 13:48 EDT