Geoffrey G. Diehl (born April 23, 1969) is an American politician from the Commonwealth of Massachusetts. A Republican, he represented the 7th Plymouth district in the Massachusetts House of Representatives from 2011 to 2019. Diehl was an unsuccessful Republican candidate for the U.S. Senate in 2018 and for governor of Massachusetts in 2022, losing both elections in landslides to Democrats Elizabeth Warren and Maura Healey respectively.