British voters are voting again for the third time in less than five years, this being the first poll in the last 100 years in December, reports the BBC.
Previous polls took place in 2015 and 2017.
Polling stations in 650 constituencies in England, Wales, Scotland and Northern Ireland opened at 7:00 GMT.
The counting of votes will start immediately after the polls close at 22:00 GMT, and most of the results will be announced in the early hours of Friday morning.
A total number of 650 MPs will be elected according to a system used for the first time in the general elections, the one in which the candidate who wins the largest number of votes in the constituency in which he is candidate wins.
In 2017, Newcastle Central was the first constituency to announce the result of the vote, about an hour after the polls closed.
Elections in the UK are traditionally held every 4 or 5 years. In October, however, parliamentarians voted for the second ballot in two years. It is for the first time after 1974 when elections take place in winter and the first time in December after 1923.
In the elections, all persons aged at least 18 years, if they are British citizens, from the Commonwealth or the Republic of Ireland, have the right to vote. Registration ended on November 26th.