After a Valencia board meeting, president Manuel Llorente said they had accepted Barca's offer for the prized striker, who scored 21 league goals last season to finish his fifth consecutive campaign as the club's top scorer.
"There was a big offer from England that was not from Chelsea but Barcelona's was the best for us and the footballer," Llorente told a news conference at the Mestalla, without specifying which Premier League club had made a bid.
"Villa has delivered a lot (to Valencia) and he deserves this chance," he added.
The 28-year-old is Spain's second-highest scorer with 36 goals from 55 matches, eight short of the record held by Real Madrid striker Raul, and he will be spearheading Spain's World Cup campaign.
Barcelona confirmed the deal in a statement on their website, saying Villa would sign a four-year contract with an option for one more year.
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