More than 46 million people are eligible to vote in what is the fourth major UK poll in three years, following the 2014 Scottish independence referendum, the 2015 general election, and the 2016 Brexit vote (to say nothing of local elections in 2014, 2015 and 2017).
Polls close at 10 p.m. UK time (5 p.m. ET), with results expected to begin rolling in within an hour or so after voting finishes.
May called the election three years earlier than scheduled ahead of what are expected to be tough negotiations with the European Union over Britain's exit from the bloc.
