Polling stations in 650 constituencies across England, Wales, Scotland and Northern Ireland will open at 7 a.m. (local time), the BBC reported.
After the polls close at 8 p.m., counting will begin straight away. Most results are due to be announced in the early hours of Friday morning.
A total of 650 MPs will be chosen under the first-past-the-post system used for general elections, in which the candidate who secures the most votes in each individual constituency is elected.
Elections in the UK traditionally take place every four or five years. But, in October, MPs voted for the second snap poll in as many years.
It is the first winter election since 1974 and the first to take place in December since 1923.
Anyone aged 18 or over is eligible to vote, as long as they are a British citizen or qualifying citizen of the Commonwealth or Republic of Ireland and have registered to vote.
Registration closed on November 26.
The two main contenders, Prime Minister Boris Johnson and opposition Labour Party leader Jeremy Corbyn, made their last election pledges on Wednesday.
In their last interviews with the BBC, Johnson repeated his main pledges, saying: "Only if you get Brexit done (can you) move the country forward."
Johnson said that he thought the election result would be "very close", and that "every vote counts".
Meanwhile, Corbyn said that there was a "greater understanding" from the public that the country "cannot go on with underfunded public services".
If there is a Labour government on Friday morning, Corbyn said the first thing he would do was "deal with the worst levels of poverty in Britain" - namely the homeless - saying: "Something must be done very quickly, very urgently and that is what we are going to do."
The two leaders also held their final rallies in London on Wednesday night.
Other party leaders also travelled the country on the last day before the election to win support from undecided voters.
Liberal Democrat leader Jo Swinson said votes for her party could stop Brexit, adding: "Our country can be better than what Boris Johnson and Jeremy Corbyn are trying to say is the only way forward."
The Scottish National Party's Nicola Sturgeon said a vote for her party was a vote to stop further cuts to public services and to "stop Scotland being dragged out of the EU against its will".
Nigel Farage warned against Johnson's deal to leave the EU, calling for voters in Leave seats to back his Brexit Party.
Green Party co-leaders Sian Berry and Jonathan Bartley urged voters to make it a moment of political reckoning on the climate, saying their party would make sure proper action was taken to meet carbon emission targets.
( With inputs from IANS )