Maria Sharapova was suspended for two years Wednesday for testing positive for meldonium at the Australian Open.
The five-time Grand Slam champion was provisionally suspended by the International Tennis Federation in early March, when she announced at a news conference in Los Angeles that she failed a doping test in January.
Sharapova said then she was not aware that the World Anti-Doping Agency had barred athletes from using meldonium, also known as mildronate, as of Jan. 1.
Her lawyer, John Haggerty, said Sharapova took the substance after that date.
Wednesday's ruling said Sharapova did not intend to cheat, but bore "sole responsibility" and "very significant fault" for the positive test.
In addition to testing positive at the Australian Open, she also failed a test for meldonium in an out-of-competition control in Moscow on Feb. 2, the ITF said.
The two-year ban can be appealed to the Court of Arbitration for Sport.
Sharapova said she first was prescribed the Latvian-made drug, typically used for heart conditions, for medical reasons in 2006. She could have been barred from competing for up to four years.
The ITF ruling in Sharapova's case follows a hearing before a three-person panel. Lawyers representing the ITF argued their side, while Haggerty argued hers. He said she spoke at the hearing.
The ban throws into doubt the on-court future of Sharapova, a 29-year-old Russian who is one of the most well-known -- and, thanks to a wide array of endorsements -- highest-earning athletes in the world.
She is a former top-ranked player who is one of 10 women in tennis history with a career Grand Slam -- at least one title from each of the sport's four most important tournaments. So much came so easily for her at the start: Wimbledon champion in 2004 at age 17; No. 1 in the rankings at 18; U.S. Open champion at 19; Australian Open champion at 20.
An operation to her right shoulder in 2008 took her off the tour for months, and her ranking dropped outside the top 100. But she worked her way back, and in 2012, won the French Open, then added a second title in Paris two years later.
Sharapova hasn't played since a quarterfinal loss to Serena Williams at this year's Australian Open, and she is ranked 26th this week.
Meldonium increases blood flow, which improves exercise capacity by carrying more oxygen to the muscles.
In April, citing a lack of scientific evidence about how long the drug remains in a person's system, WADA said that provisional suspensions may be lifted if it is determined that an athlete took meldonium before it went on the list of banned substances.
About 200 athletes tested positive for meldonium this year from various sports and countries -- many, like Sharapova, were Russian -- and some said the drug stayed in their systems for months even though they stopped using it in 2015.
But, according to Haggerty, that was not the case for Sharapova.