Voting is under way in the UK at more than 40,000 polling stations across the country.
Polls opened at 07:00 BST on June 8, with counting starting once voting ends at 22:00 BST.
A total of 650 Westminster lawmakers will be elected, with about 46.9 million people registered to vote.
Some votes have already been cast, through postal voting, which accounted for 16.4% of the total electorate at the 2015 general election. People with an undelivered postal vote can still deliver it by hand to their local polling station.
Two years ago, when the Conservatives won 331 out of 650 seats, overall turnout was 66.4%, up from 2010.
Most polling stations are in schools, community centers and parish halls, but pubs, a launderette and a school bus have been used in the past.
Police have increased security at polling stations, including patrols by armed officers in some areas, following the recent terror attacks.
A handful of seats are expected to be declared by midnight, with the final results expected on June 9.
Unusually, no local elections are taking place at the same time, so results might come through earlier than in recent general elections.
In 2015, the first seat to declare was Houghton and Sunderland South, at 22:48 BST.
To form a majority in the House of Commons one party must win 326 seats – in 2015 a Conservative majority was not confirmed until 13:34 BST.
Polls close at 22:00 BST, but officials say anyone in a polling station queue at this time should be able to cast their vote.