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 in the Johnson government from 2019 to 2022. A member of the Conservative Party, he has been the Member of Parliament (MP) for Carmarthen West and South Pembrokeshire since 2010.

The Chief Whip of the Conservative Party oversees the whipping system in the party, which is responsible for ensuring that Conservative MPs or members of the House of Lords attend and vote in parliament in the desired way of the party leadership. Chief Whips, of which two are appointed in the party, a member of the House of Commons and a member of the House of Lords, also help to organise their party's contribution to parliamentary business.