Simon Mayne[1] (1612 – 13 April 1661) was a Member of Parliament for Aylesbury and one of the regicides of King Charles I of England.
His father died when he was aged five, leaving him the Dinton Hall estate after the death of his mother (in 1629).
He was educated at Thame in Oxfordshire at Lord Williams's School and admitted to the Inner Temple in 1630.
In January 1649, as a judge of the High Court of Justice at the trial of King Charles, he was 40th of the 59 signatories on the death warrant of the monarch.
The estate was inherited by his son, Simon Mayne, who also represented Aylesbury in Parliament and was a commissioner of victualling under William and Mary.