Kilmarnock and Loudoun is a county constituency of the House of Commons of the Parliament of the United Kingdom.

The constituency consists of the northern and central areas of East Ayrshire and contains the town of Kilmarnock and the Irvine Valley.

There was a Kilmarnock and Loudoun local government district covering a similar area, from 1975 to 1996.

Under the 2023 review of Westminster constituencies, which came into effect for the 2024 general election, the boundaries were unchanged.

[2] Further to reviews of local government ward boundaries which came into effect in 2007 and 2017, but did not affect the parliamentary boundaries, the contents of the constituency are now defined as comprising the following electoral wards of the East Ayrshire council area:[3][4][5] The main towns and villages are: Those towns marked * were not part of the original Kilmarnock and Loudoun, but were absorbed from the disbanded Carrick, Cumnock and Doon Valley.