Britain's Prime Minister Rishi Sunak, from the Conservative Party, has called a surprise general election for July 4.
Legally, a vote did not need to be held until late January next year.
Mr Sunak's Conservatives, which have been in government since 2010, have trailed the opposition Labour Party in every opinion poll published since January 2022.
"Over the next few weeks I will fight for every vote, I will earn your trust, and I will prove to you that only Conservative government led by me will not put our hard-earned economic stability at risk, can restore pride and confidence in our country, and with a clear plan and bold action we will deliver secure future for you, your family and our United Kingdom," the PM said outside his official London residence, 10 Downing Street, just after 5pm local time on Wednesday.
As he spoke, rain tumbled down and protesters played D:Ream's 1993 hit "Things Can Only Get Better" on loudspeakers.
Since they've been in power, the Conservatives - colloquially known as the Tories - have churned through five prime ministers: David Cameron, Theresa May, Boris Johnson, Liz Truss and Mr Sunak.
Labour, led by Sir Keir Starmer, is considered the clear frontrunner for the election and a YouGov poll published in The Times newspaper last week put its lead at 27 percentage points.
Shortly after the PM's announcement, Sir Keir made a brief statement in central London in which he described the past 14 years as "Tory chaos" and said it was "time for change".
"So here it is, the future of the country in your hands, on the fourth of July you have the choice and together we can stop the chaos, we can turn the page, we can start to rebuild Britain and change our country," Sir Keir said.
Mr Sunak had repeatedly said that the election would be called in the second half of 2024 and said so again when asked about it in the parliament on Wednesday local time.
Mr Sunak took over from Ms Truss, who had been in office for just 49 days, in late 2021.
Most pundits had forecast the election to be called for October or November. The last UK election was held in December 2019.
However, better-than-expected inflation figures, as well as economic data suggesting the country had emerged from a recession, gave the government something to highlight.
Progress on a key policy might also have prompted the call for an early poll.
Mr Sunak had celebrated progress in recent weeks on a blueprint to deport migrants who arrive in the UK by boat, to Rwanda.
On top of immigration and the economy, other key issues the campaign is expected to be fought on include the state of the country's health system and cost of living.
The general election will be for Britain's lower chamber of parliament — the House of Commons — and its 650 seats. The UK's upper house is completely unelected.
The Conservatives currently hold 344 seats in the commons.
While Labour is the main opposition party with 205 seats, the centre-left Scottish National Party (SNP) (43 seats), and centrist Liberal Democrats (15 seats) — who formed a coalition to deliver the Tories power in 2010 — are considered the other major players.
Liberal Democrats leader Sir Ed Davey was buoyant at his party's prospects at the election.
"In so many parts of the country, it's the Liberal Democrats who can beat the Conservatives," he said after the announcement.
SNP leader and Scotland's First Minister John Sweeny was surprised at the timing of the election.
"It's a wee bit sooner than I think everybody thought, but it's welcome," he said.
"It's a welcome opportunity to remove the Tory government and to put Scotland first."
In Northern Ireland, the right-wing Democratic Unionist Party holds seven seats, while left-wing Irish republican party Sinn Fein also has seven but its MPs do not take up their positions in Westminster as part of a policy of abstentionism.
After the election date was announced, Buckingham Palace released a statement saying the Royal family had postponed engagements "that may appear to divert attention" from the campaign.