Ms May pledged several times after taking office last year not to call an early election, so this is something of a U-turn.
A victory in June would also hand her a very important personal mandate. Having taken over from Mr Cameron when he resigned mid-term, after losing the Brexit referendum, she has yet to win her own general election.
Who is Theresa May?
The 59-year-old served for 17 years in senior positions within the Conservative party before becoming leader, and is said to have harboured ambitions at a young age to be the first female prime minister.
She is the country’s second, following Margaret Thatcher.
Ms May said she would put the election to a vote on Wednesday. If it passes, parliament will be dissolved 25 days before the election, on 3 May, for official campaigning to start.
The Labour party has said it supports the outcome of the Brexit referendum, and only the small Liberal Democrat party has expressed a desire to overturn the vote.
But there has been disagreement in parliament over the terms of the exit, and an improved majority will give Ms May more leverage and help to quell arguments among her own MPs.