Loudoun () applies to both a parish and earldom in East Ayrshire, Scotland. The latter title is now honorific, and both the parish and earldom had different landed extents attached to them. Loudoun 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.
The historical Loudoun parish 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. Some parts of Galston parish comprised parts of the historical Earldom of Loudoun. Otherwise, Loudoun shares borders with the parishes of Avondale (east), Eaglesham (north), East Kilbride (north-east), Fenwick (north-west) and Kilmarnock (west).
Within the Loudoun territory 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.
Etymology
thumb|200px|left|[[Loudoun Castle
]]Various suggestions have been put forward as to the origins of the name Loudoun. An older antiquarian hypothesis is that the name was originally used in reference to Loudoun Hill - being a combination of two Scots words lowe and dun, which roughly translates as fire hill. However, 'dun' in this context would strictly refer to a site of Iron Age or Early Medieval, Celtic-type fortification, often situated on easily defensible hills. This is historically incompatible in a linguistic construction sense with the Old English low/lowe, and so this idea is not logically sound.
A more secure past analysis, which also centres on the hill locus, is Lugudunon, translating from Old Celtic as the fortified residence of Lugh or Lugus. The latter is a pan-Celtic deity of light (or darkness) associated with prominent hills, solar events, or seasonal changes. It has also been speculated that the name derives from the Celtic word, Loddan for marshy ground, although this place-name does not seem justified as a distinct district identity, given it was a generic topographical descriptor.
History
Whilst the origins of Loudoun's name may remain debateable, it is known that by 1186 the name was used for the surrounding area, for in that year a Royal Charter was issued that granted the Lands of Lowdun to James de Lambinus. At this time the family name was changed to de Lowdun, with the Loudoun family building Loudoun Castle, Loudoun Kirk and The Keep (in Newmilns) over subsequent centuries.
Subsequently, the Loudoun family married in to the Crawford family and in doing so inherited the hereditary title 'Sheriff of Ayr'.