Over 4,700 council seats are up for grabs in England, while every seat in Scotland’s 32 unitary authorities and the make-up of Wales’ 21 authorities are also being voted on.
Polling stations opened at 0700 this morning, and will close at 2200 tonight. Results are expected to come in through tomorrow.
Meanwhile mayors are being elected in London, Liverpool and Salford, while there are referendums on whether to have elected mayors in ten other areas, including Nottingham, Newcastle and Bristol.
Doncaster will be voting on whether to abolish their mayor, whom they voted to introduce eleven years ago.
In London, sitting mayor Boris Johnson is fighting for a second term, while strong challenges from former mayor Ken Livingston and Brian Paddick. Other candidates include independent Siobhan Benita, the BNP's Carlos Cortiglia, the Green Party's Jenny Jones and UKIP's Lawrence Webb are also standing.
A total of twelve candidates are up for the role of mayor in Liverpool, while ten people are fighting for the job in Salford.
There are also elections for the London Assembly being held for the first time since 2008.