Simon Anthony Hart is a British politician serving as the Chief Whip of the House of Commons and Parliamentary Secretary to the Treasury since October 2022. He previously served as Secretary of State for Wales between 2019 and 2022. A member of the Conservative Party, he was first elected in the 2010 general election as the Member of Parliament (MP) for Carmarthen West and South Pembrokeshire, defeating the previous Labour MP Nick Ainger who had represented the constituency and its predecessor since 1992. He was reelected in 2015, 2017 and 2019 general elections.