Sharapova, 28, said that she has been taking the drug Meldonium since 2006 but it was banned by the World Anti-Doping Agency in January.
Meldonium is designed to treat chest pain and has been shown in some tests to increase endurance in patients. The drug is not approved by the U.S. Food and Drug Administration but it is approved for use in Russia.
"For the past 10 years I have been taking a medicine called mildronate by my doctor, my family doctor, and a few days ago after I received the letter from the ITF [International Tennis Federation] I found out it also has another name of Meldonium, which I did not know," Sharapova said at a press conference today.
"It is very important for you to understand that for 10 years this medicine was not on WADA's [World Anti-Doping Agency] banned list and I had been legally taking that medicine for the past 10 years.
"But on [Jan. 1] the rules had changed and Meldonium became a prohibited substance, which I had not known."
The Russian player is currently ranked No. 7 in the world by the Women's Tennis Association and holds five championship titles.
Sharapova has been listed by Forbes as the highest-paid female athlete in the world for the past 11 years. The magazine reported that she earned $29.5 million in 2015.
"I know that with this I face consequences and I don't want to end my career this way. I really hope to be given another chance to play this game," she said today.
Her team announced the press conference and teased a "major announcement" which led some to speculate about Sharapova potentially announcing her retirement from the sport, but she was quick to put that to rest.
"I know many of you thought that I would be retiring today but if I was ever going to announce my retirement it would not be in a downtown Los Angeles hotel with this fairly ugly carpet," she said.