Five-time Grand Slam champion Maria Sharapova has announced her retirement.

"Tennis -- I'm saying goodbye," she wrote in an essay that appeared Wednesday in Vogue and Vanity Fair.

Sharapova turned pro in 2001 at age 14. She won Wimbledon in 2004, the US Open in 2006, the Australian Open in 2008 and the French Open in 2012 and 2014. She is one of only six women in the professional era to win each major tennis title at least once. She made 10 Grand Slam finals in all, going 5-5.

For a while, Sharapova was as big a star as her sport had, earning many more millions of dollars in sponsorship deals than she did on the court.

The 32-year-old Russian reached No. 1 in the WTA rankings in 2005, 2007, 2008 and 2012, but she has dropped to No. 373. She lost in the first round of this year's Australian Open to Croatia's Donna Vekic in straight sets. She played only two matches this season and lost both.

"Throughout my career, Is it worth it? was never even a question -- in the end, it always was," she wrote. "My mental fortitude has always been my strongest weapon. Even if my opponent was physically stronger, more confident -- even just plain better -- I could, and did, persevere."

She disclosed that she "had a procedure to numb my shoulder to get through the match" a half-hour before walking on court for a first-round exit at last year's US Open, writing: "I share this not to garner pity, but to paint my new reality: My body had become a distraction."

Sharapova burst onto the tennis scene at 17 by upsetting Serena Williams to win Wimbledon in 2004. She would beat Williams again at that year's season-ending tour championship to improve to 2-1 against the American -- and never won another one of their matchups, dropping the next 19.

Maria Sharapova, who has been playing professional tennis since 2001, said in an essay she wrote for Vogue and Vanity Fair that she is retiring. Hannah Peters/Getty Images

Sharapova received a two-year suspension from the International Tennis Federation in 2016 for testing positive for the banned substance meldonium. The suspension was reduced to 15 months by the Court of Arbitration for Sport after Sharapova appealed. The CAS said there was "no significant fault" by her.

"In so many ways, I feel like something I love was taken away from me, and it will feel really good to have it back," Sharapova said in a statement after her successful appeal.

After that suspension, Sharapova managed to reach only one major quarterfinal.

Shoulder injuries hampered her career, and she had multiple surgeries.

Sharapova compiled a 645-171 singles record that included 36 titles.

"Tennis showed me the world -- and it showed me what I was made of. It's how I tested myself and how I measured my growth," Sharapova tweeted Wednesday. "And so in whatever I might choose for my next chapter, my next mountain, I'll still be pushing. I'll still be climbing. I'll still be growing."

The Associated Press contributed to this report.