Martyn Underhill MBE is a British independent politician and former police officer who served as the Dorset Police and Crime Commissioner from 2012 to 2021. He was a Detective Chief Inspector in Sussex Police, who retired in 2009 after 30 years of service. He joined the Metropolitan Police in 1979, transferring to Sussex Police in 1984. He was a Constable in the Metropolitan Police during the existence of the Special Demonstration Squad [1968 - 2008].