It is the largest prize pool in the history of e-sports, with $30m shared amongst the winners.
Kyle Giersdorf, 16, won the solo event of the competition in the Arthur Ashe Stadium in New York, which hosts the US Open tennis tournament.
British teenager Jaden Ashman won almost £1m for coming second in the duos event.
Mr Giersdorf, known online as Bugha, stood laughing and shaking his head as the crowd erupted when his name was announced.
He told the BBC he wants to save most of his prize. "All I want is a new desk and maybe a desk for my trophy," he said.
The final game was described by the commentators as a "ridiculous victory lap" as the winner played with a smile on his face whilst beating his rivals.
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