2017 United Kingdom General Election June 08,2017 - All You Need To Know
The polls are open from 7:00am (0600 GMT) until 10:00pm (2100 GMT) on June 8.
British, Irish and Commonwealth residents aged 18 and over can vote, plus British citizens and Irish citizens from Northern Ireland living abroad who have been registered to vote in the UK within the last 15 years.
Citizens must register to vote and voting is not compulsory.
There are 650 constituencies across the UK, meaning 326 MPs are needed for an absolute majority in parliament's lower House of Commons.
May had a slim working majority of 17 at the dissolution of the last parliament and called the election in a bid to strengthen her position going into the Brexit talks.
Each constituency is won on a first-past-the-post basis, meaning the candidate with the most votes in that seat becomes its MP.
Despite the focus on the party leaders, voters are not directly choosing their prime minister, only their local MP.
The main parties across the whole of Britain are the Conservatives (centre-right), led by May, and Labour (left), led by Jeremy Corbyn, followed by the Liberal Democrats (centre-left), the UK Independence Party (populist) and the Greens (left).
The Scottish Nationalists (left), Welsh nationalists Plaid Cymru (left) and four parties from Northern Ireland also won seats at the last general election in 2015.
Polls suggest the Conservatives are on course for victory. However, Labour might be able to form a government with backing from smaller left-wing parties.
The main issues are Brexit, terrorism, the state-run National Health Service, immigration and the economy, according to polls.
Some 3,303 candidates are standing. A £500 deposit is required to stand, which is refunded if candidates get five percent of the votes cast.
A parliament is elected for a maximum of five years, meaning the next general election must be held by June 2022 at the latest.
Key points from the manifestos of the main parties
Conservatives: Prime Minister Theresa May has already outlined her negotiating demands, saying she will seek a departure from the European Union's single market and an end to free movement of people.
Labour: The party will accept Britain's departure from the European Union, but will fight to retain benefits of the single market, vowing in its manifesto not to leave the bloc without a deal.
Liberal Democrats: The Lib Dem manifesto provides the strongest opposition to Brexit, promising to hold a second referendum on a final Brexit deal and to maintain free movement of people with the continent.
If the Brexit deal is rejected in a second referendum, the Lib Dems say Britain would stay in.
Scottish National Party (SNP): The party wants a referendum on independence before Britain actually leaves the bloc and has said an independent Scotland would then re-apply to join the bloc.
First Minister Nicola Sturgeon also wants a seat in Brexit negotiations and for Scotland to be given special status to be allowed to stay in the single market even if the rest of Britain leaves.
UKIP: The deeply eurosceptic, anti mass-immigration party has promised to ban the flying of the EU flag on public buildings and to push the government into not paying for any divorce settlement with the bloc
Conservatives: The Tories will try to reduce annual net migration to the tens of thousands, down from 248,000 in 2016 although some senior party figures are sceptical whether this can be achieved.
May has promised that Britain will end freedom of movement with European citizens following Brexit.
Labour: Jeremy Corbyn's party has made no pledge to reduce immigration, saying in its manifesto that it "believes in fair rules and reasonable management of migration".
Lib Dems: The Lib Dems manifesto puts no target on immigration levels, and calls to remove students from official migration statistics.
SNP: The party's manifesto calls for the devolution of immigration powers to Scotland to allow immigrants from the European Union to continue to come.
UKIP: The party advocates a "one in, one out" immigration system and pledged to reduce net migration to zero over a five-year period
HEALTH & SOCIAL CARE
Conservatives: May announced controversial plans for the elderly to pay for their own care costs if they have assets worth more than £100,000 ($128,600, 114,000 euros).
The reforms were immediately called the "dementia tax", forcing May to announce there would be a cap on the total amount any one person would pay, coinciding with a plunge in her polling lead.
Labour: The party has pledged £30 billion of extra funding for the National Health Service and £8 billion for care services over the next parliament.
Independent think-tank the IFS has said the tax rates needed to fund Labour's spending plans would be the highest for Britain in peacetime.
Conservatives: The election has been overshadowed by three assailants hitting pedestrians and going on a stabbing rampage in the popular London Bridge area on Saturday in which seven people were killed, Britain's third attack in three months.
May has insisted that the Conservatives have increased counter-terrorism policing resources and has defended her decision to cut thousands of police jobs during her time as interior minister.
On Sunday she promised to clamp down on Islamist extremism, particularly with more online regulation.
Labour: Corbyn has promised to fund an extra 10,000 police officer jobs. He said more community policing will increase "detailed local knowledge and build a network of relationships".