The former New Zealand cricket captain Chris Cairns has been awarded £90,000 in damages after allegations on Twitter that he was involved in match-fixing.
Mr Cairns, 41, sued Lalit Modi, the former chairman of the IPL, the Twenty20 franchise in India.
Mr Modi has so far refused to apologise for the allegation he made in a tweet.
Mr Cairns's lawyer said the comments had tainted the career of his client, who played for Nottinghamshire before a spell in India.
It is the first Twitter libel case in England. Last year a councillor in Caerphilly, Wales, was ordered to pay £3,000 and costs to a political rival for posting a libellous comment on Twitter.
Mr Modi was also ordered to pay Mr Cairns' £400,000 legal costs.
Mr Cairns, who took more than 200 wickets and scored more than 3,000 runs in 62 Test matches, said Mr Modi's tweet in January 2010 was an "unequivocal allegation".
He was not at the High Court in London for the ruling by Mr Justice Bean.
But later he made a statement, saying: "I feel great relief that I am (now) able to walk into any cricket ground in the world with my head held high."
The judge, who sat without a jury, said Mr Modi had "singularly failed" to provide any reliable evidence Mr Cairns was involved in match-fixing.
He said: "It is obvious that an allegation that a professional cricketer is a match-fixer goes to the core attributes of his personality and, if true, entirely destroys his reputation for integrity.
"The allegation is not as serious as one of involvement in terrorism or sexual offences (to take two examples from recent cases). But it is otherwise as serious an allegation as anyone could make against a professional sportsman."
The court was told Mr Modi's tweet was picked up by cricket website Cricinfo, who withdrew its report, paid damages and apologised after Mr Cairns complained.
But Mr Modi declined to apologise and pleaded justification, maintaining the allegation was true.
Mr Cairns said the allegation was "wholly untrue" and could destroy the reputation he built up during a 20-year career.
Mr Cairns captained the Chandigarh Lions in 2007/8 in the Indian Cricket League (ICL), a rival to Mr Modi's IPL.
Lawyer and defamation expert Niri Shan, a partner at Taylor Wessing, said: "'This case demonstrates that posts on Twitter are taken as seriously, in the eyes of the law, as comments printed in mainstream press.
"Whilst people may feel less cautious about tweeting- the level of risk they are taking, and protection of those being referred to, remains the same.
"The fact that this will have cost Lalit Modi over £1m, if both sides' costs are accounted for, reinforces the point of how careful people should be."
'Lifts a dark cloud'
After the ruling, Mr Cairns said: "Today's verdict lifts a dark cloud that has been over me for the past two years. I feel mixed emotions.
"Firstly, sadness that I should ever have had to put myself, my friends and my family through this because of one man's misdirected allegations.
"But I also feel great joy because my past career has come through unscathed and remains intact and because I had the courage to stand up in the highest court to defend my name.
"Lastly, I feel great relief that I am able to walk into any cricket ground in the world with my head held high."
The judge granted Mr Modi permission to appeal over the amount of damages but refused permission on the question of liability. However, it is understood Mr Modi's lawyers wish to pursue that application directly with the Court of Appeal.
Judge Bean rejected a claim by Mr Modi's lawyer, Ronald Thwaites QC, that the action amounted to "libel tourism".
He pointed out Cairns' children went to school in England, that he had played county cricket for seven seasons, and that Mr Modi had lived in the UK since the summer of 2010.
Cricketers Gaurav Gupta, Rajesh Sharma and Tejinder Pal Singh gave evidence on behalf of Mr Modi but the judge said it was not to be believed and he said hearsay evidence from two other players, Amit Uniyal and Love Ablish, was "inconsistent and unreliable".
"Even if I were applying a simple balance of probabilities test, the plea of justification would fail in both respects," he said.
The judge said he had increased the damages from the starting point of £75,000 to £90,000 to reflect the "sustained and aggressive" actions of Mr Thwaites, who had used the words "lie", "liar" and "lies" 24 times in his closing speech.