The polls open at 7am today for the biggest set of elections outside a general election in almost 50 years.
Voters will cast their ballots despite the many COVID-19 restrictions still in place, with 48 million people given the chance to have their say.
In Scotland and Wales, the electorate will decide on their national representatives in Holyrood and the Senedd respectively. In Wales, young people aged 16 and over will get the chance to vote for the first time.
Elsewhere there are a total of 143 different councils running elections today, while in Hartlepool voters are deciding who should represent them in Westminster.
There are also 13 mayoral elections, including for the London mayor, and 39 police and crime commissioner elections across England and Wales after these votes were postponed in 2020 because of the pandemic.
COVID-19 is still having an effect on voting today, with strict limits on how many people can be inside a polling station, face masks required and social distancing for those volunteering to help out.
People have also been told not to offer anyone outside of their bubble a lift to the polling station, something political parties usually do to encourage people to vote.
Experts predict many more people will have applied for a postal vote this year because of the restrictions.
Polls will close at 10pm and you do not need a polling card to vote, though you must be registered.
The results will emerge in the coming days, with some not expected until late on Sunday.