The election on Thursday is one of four across the UK, with the other ballots in Stoke-on-Trent, Hackney in east London, and Bedford.
The polls open at 0800 BST on Thursday and close at 2000 BST.
About 78,000 residents are eligible to vote, and the final results are expected sometime after midnight.
Mayoral candidates
Kate Allsop, Conservative
Lorna Carter, Labour
Phillip Smith, Lib Dem
Michael Comerford, Green
Tony Egginton, Independent
After decades in power in Mansfield, the Labour Party is being challenged by the Conservatives, Liberal Democrats, the Green Party and an independent.
The mayor will have the power to appoint a cabinet, the decision-making heart of the council, and will be expected to carry out election pledges.
The referendum was the result of a campaign headed by local businessman Stuart Rickersey, who organised a petition of 4,000 signatures.
He said it was time for a change in the way the council was run.
Turnout at the referendum was 21%.
There are 83 polling districts in the town, with most of them located in schools, meeting halls and churches.
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