Killough (/kɪˈlɒx/ ki-LOKH; from Irish Cill Locha, meaning 'church of the loch')[1][2] is a village and townland in County Down, Northern Ireland.

[7] After the outbreak of war between Great Britain and France in 1793 the growing of cereals increased in Lecale and Killough, as one of the ports of export, expanded to deal with it, until its population was almost double what it is today.

A report in 1822 comments on the considerable corn and coal trade and the 22 yawls which "afford the chief supply of white fish to the county of Down.

"[8]: 105 The existing harbour facilities were soon inadequate and between 1821 and 1824, Michael Ward's son, the first Lord Bangor, employed the engineer Alexander Nimmo, to build new quays[8]: 71  at a cost of £17,000.

The village prospered and the grain merchants built their imposing houses in Castle Street, and their stores on the narrow lane leading to the quays.

[8]: 29 In September 1981 an off-duty police officer, Sandy Stewart, was shot dead by the IRA in the Ann Boal Inn.

[9][10] Killough is classified as a small village or hamlet by the Northern Ireland Statistics and Research Agency (NISRA).