"Tennis - I'm saying goodbye," she said in Vogue and Vanity Fair magazine article.
"After 28 years and five Grand Slam titles, though, I'm ready to scale another mountain - to compete on a different type of terrain," she added.
Sharapova burst onto the scene as a supremely gifted teenager and won her Grand Slams before serving a 15-month ban for failing a drugs test at the 2016 Australian Open.
The Russian former world number one's ranking is currently 373rd.
Sharapova has hardly played in the past year because of long-standing shoulder problems.
When she did play she lost as many matches as she won and was dumped out in the first rounds at Wimbledon, the US Open and, most recently, the Australian Open in Melbourne.
Sharapova shot to fame as a giggly 17-year-old Wimbledon winner in 2004, the third-youngest player to conquer the All England Club's hallowed grass courts.
She became world number one in 2005 and won the US Open the next year.
"One of the keys to my success was that I never looked back and I never looked forward," Sharapova said on Wednesday.
"I believed that if I kept grinding and grinding, I could push myself to an incredible place."
But in 2007 Sharapova began her long on-off battle with shoulder trouble.
She would win the 2008 Australian Open before a second shoulder injury kept her off tour for the second half of the season, missing the US Open and Beijing Olympics.
In 2012, the Siberian-born Sharapova captured the French Open to become the 10th woman to complete a career Grand Slam. She added Olympic silver to her resume that year.
Her 2014 French Open title was another high after a dispiriting injury low.
More fitness troubles followed before the bombshell announcement of her positive test for the banned heart drug meldonium.
Always a fighter -- the seven-year-old Maria and father Yuri left for the US in 1994 with just a borrowed $700 to their names -- Sharapova returned to the sport in 2017.