The PM made the announcement in a rain-soaked speech outside 10 Downing Street, as he bids to win a fifth term in office for the Conservatives.
The surprise move overturned expectations of an autumn poll, which might have given the Tories a better chance of closing the gap with Labour.
Sir Keir Starmer said it was "time for change" away from "Tory chaos".
Labour has been posting large leads in national opinion polls, and has insisted it has a fully organised campaign ready to go.
Parliament will now be suspended on Friday, before it is formally shut down on Thursday next week ahead of an official five-week election campaign.
It means there are only two days to pass any outstanding legislation - a move which will mean some of the government's measures will have to be abandoned.
October or November had previously been thought more likely for an election date.
AzVision.az
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