Argentina's Mariano Puerta has been banned from competition for eight years after failing a doping test following this year's French Open final.
The International Tennis Federation confirmed the 27-year-old had tested positive for the banned stimulant etilefrine after his final defeat.
He is now banned from June 2005 and will forfeit ranking points and £300,000 in prize money.
Puerta now has three weeks to appeal against the decision.
The ruling was handed out after an independent tribunal, convened under the ITF anti-doping programme, found that Puerta had tested positive.
He was in line for a life ban but because the positive result was "caused by an inadvertent administration of etilefrine", a lighter suspension was given.
"The tribunal rejected a defence of no fault or negligence, but accepted an alternative plea of no significant fault or negligence," said the ITF.
Puerta claimed the drug entered his body just before the final after he inadvertently used a glass that had previously been used by his wife, who takes a treatment containing etilefrine.
The current world number 12, who lost the final 6-7 6-3 6-1 7-5 to Spain's Rafael Nadal, will also give up his titles and prize money won after the French Open.
His place as runner-up will be kept on the record books.
Two years ago, Puerta was banned for nine months by the ATP for taking the banned anabolic steroid clenbuterol.
In a statement released through his solicitors, Puerta said: "My position has always been that I did not deliberately or knowingly ingest any prohibited substance.
"The Tribunal's Decision and its reasoning upholds and confirms this to be the case."
The ITF sanction was welcomed by World Anti-Doping Agency chief Dick Pound.
"Somebody who has tested positive twice in less than two years is someone who clearly doesn't think the rules apply to them," he said.
"I know that the ITF have been working for a number of years in the interests of the sport and the process is now more transparent.
"The testing regimes will get better over time and the deterrent effect of these kind of sanctions where positive cases are discovered will I hope persuade players who might otherwise consider using these drugs not to do so.
"It is a big, big step forward. We're very pleased with (the Puerta verdict) and we will keep working with the ITF to help them make their sport even cleaner."
The French Tennis Federation was also pleased with the suspension but stated that the issue should have been dealt with more quickly.
"The FFT welcomes the fact that the rules in the anti-doping programme of the ITF have been implemented by the tribunal which was dealing with a case of second offence," said a statement.
"The FFT and its chairman Christian Bimes ask for the disciplinary procedure to be shortened.
"The standard procedure lasts up to six months. This lapse of time should be reduced to three or four months."
The Argentine Tennis Federation has admitted it is probably the end of the road for Puerta.
"With such a sanction, I think that it is the end of his career," said Enrique Morea, the federation president.
"It's very sad news. I don't know what to say because there has never been such a serious suspension in tennis before."