Loudoun (Scottish Gaelic: Lughdan) is a parish in East Ayrshire, Scotland and lies between five and ten miles east of Kilmarnock. The parish roughly encompasses the northern half of the Upper-Irvine Valley and borders Galston Parish (which encompasses the remainder of The Valley) at the River Irvine.
Loudoun is a parish, which shares borders with six other parishes. To the south lies the parish of Galston, which of all the surrounding parishes, has the strongest local links to Loudoun, being as the two parishes share strong historical and social links, as well as sharing public services. Otherwise, Loudoun shares borders with the parishes of Avondale (east), Eaglesham (north), East Kilbride (north-east), Fenwick (north-west) and Kilmarnock (west).Within Loudoun can be found the towns of Darvel and Newmilns, alongside Loudoun Hill, Loudoun Castle, Loudoun Kirk and Loudoun Academy. Notably, claims that Greenholm, Priestland and the town of Galston itself lie within Loudoun are erroneous, as all three lie south of the River Irvine, in the parish of Galston. This may in some part be because Loudoun Academy and surrounding housing hold Galston postcodes.
Loudoun also contained two villages abandoned during the last century, Alton and Loudoun Village.