Party leaders from across the political spectrum have been casting their votes in their constituencies around the UK.
Conservative leader David Cameron, Labour leader Ed Miliband, Liberal Democrat leader Nick Clegg, Greens leader Natalie Bennett, UKIP leader Nigel Farage, SNP leader Nicola Sturgeon, and Plaid Cymru’s Leanne Wood have all cast their votes.
Around 50,000 polling stations opened at 07:00 BST, and will remain open until 22:00.
The results will be declared throughout the night as the votes are counted, with the first results expected to be confirmed at around midnight.
Fifty million people have registered to vote to elect 650 Westminster MPs in one of the most hotly contested general elections in decades.
Around 15% of the electorate chose to make postal votes in the 2010, and a similar number is expected in this election.
Alongside the general election, more than 9,000 council seats are being contested in 279 local authorities in England. Mayors are also up for election in Bedford, Copeland, Leicester, Mansfield, Middlesbrough, and Torbay.