Loudoun is a parish, which lies in East Ayrshire Council Area, some 4 miles (6 km) northeast of Galston and 8 miles (13 km) east of Kilmarnock in East Ayrshire.
It is located in the old county of Ayrshire, which disappeared following the Local Government (Scotland) Act 1974.
The parish has an area of 62.9 sq. km (24.2 sq. miles). Loudoun has 6 neighbouring parishes; namely Avondale, Eaglesham, East Kilbride, Fenwick, Galston and Kilmarnock.