She said Britain needed certainty, stability and strong leadership following the EU referendum.
Explaining the decision, Mrs May said: "The country is coming together but Westminster is not."
There will be a Commons vote on the proposed election on Wednesday - Labour have said they will vote with the government.
The prime minister needs Parliament's backing to hold a vote before the next scheduled date of 2020.
Explaining her change of heart on an early election, Mrs May said: "I have concluded the only way to guarantee certainty and security for years ahead is to hold this election."
***Un jour, ça ne vous suffit pas, un jour pareil aux autres il est devenu muet, un jour je suis devenu aveugle, un jour nous deviendrons sourds, un jour nous sommes nés, un jour nous mourrons, le même jour, le même instant, ça ne vous suffit pas ?