Belcoo (/bɛlˈkuː/ (from Irish Béal Cú, meaning 'mouth of the narrow [stretch of water]') is a village and townland in County Fermanagh, Northern Ireland, 10 miles (16 km) from Enniskillen. It is on the County Fermanagh/County Cavan border beside the village of Blacklion in the Republic of Ireland. It had a population (with Holywell) of 439 in the 2021 census. It is situated within the Fermanagh and Omagh District.

The Lough MacNean Tourism Initiative has been in operation since 2003, and is an economy building project, aimed at addressing tourism needs in the area while promoting cross-border relations. Belcoo Enterprise Ltd opened in 1992 in units shared with the Belcoo Historical Society, a doctor's surgery, a chiropodist and Lakeland Community Care. The Mullycovet corn mill, which functioned from 1830 until the 1920s, is being restored. The Indigenous Resources School of Transferable Skills aims to teach marginalised groups including the unemployed, New Age travellers, the disabled, to use natural materials as a learning facility.

The earliest mention of the village is in the old Ulster Saga "Argain Belcon Breifne" also known as "Togail Bruidne Bélchon Bréifne" (Massacre of Belcu Brefne). This tells the tale of a trap set for the great Ulster hero Conall Cernach by a Breifne chief named Belcu Brefne. However Conall manages to reverse the trap and causes Belcu's sons to kill Belcu by mistake. The place where the tale occurs was later named Belcu or sometimes Belcon in honour of Belcu. Isaac Butler in his book "A Journey to Lough Derg" written in c. 1749 states-

At Bell Con in this Neighbourhood on the road to Sligo is a famous Well called Davagh Patrick, or the holy Well it is found by repeated Experience to be the best Cold Bath in the Kingdom, having received Numbers in nervous & paralitic Disorders, & is coming into great request, it is exceeding transparent & so intensely cold that it throws one into a shaking Fit by putting one's hand into it, it exhibits a Stream that turns 2 mills at 150 Yards from the Spring. In April & May succeeding the great Frost in 1740 happened an Accident that gave Birth to a Miracle at this Spring but they could not ascribe the Saint without it was St. Patrick; the water was changed into the Color of Milk & as it was of a fine solf nature it quickly gained the repute of being milk by the Vulgar who flockt from all parts to see it they could not be convinced to the Contrary until it ceased, it continued 7 Weeks. Father O Mulloy thus accounted for it, that the adjacent lands were full of marly bottoms, that this Spring having it's Channel thro those beds of Marl, upon the breaking of the Frost, the marl was loosened & fell into the Spring and gave it the tincture which subsiding it returned to its usual Transparency & then the Wonder ceased."

See "Dabhach Phádraig: St Patrick's Holy Well, Belcoo, County Fermanagh", by Mairead O'Dolain, in the Clogher Record, Volume 18, No. 1, pp. 103–116. (viewable on JSTOR).

A modern interpretation however states that the name of the village derives from the Irish: béal meaning mouth and cumhang or cung meaning narrowing, referring to the village's position on a narrow neck of water (river) between Upper and Lower Lough MacNean. This interpretation is given support, firstly in the 14th century Book of Magauran where it is mentioned several times as Cunga, secondly in an Inquisition held at Dromahair on 22 July 1607 which described the boundaries of County Leitrim inter alia as- and so to Beallacowngamore, and then to Beallucowngabegg, and thirdly by the name of the place on the 1609 Ulster Plantation map where it is named 'Kiliconge', i.e. Coille Cunga meaning "The Wood of the Narrow Strip of Land". The townland to the immediate north of Belcoo continues this interpretation as it is called Drumcoo, i.e. The Hill of the Narrow Strip of Land. Another often used derivation is Béal Cú i.e. where Cú is the word for hound. Hence the village name would mean "The Mouth of the Hound". Máire MacNeill in her book "The Festival of Lughnasa", 1962, gives a local Belcoo folktale about balefire coming out of a hound's mouth before it is killed by Saint Patrick. This tale is also found in Glangevlin folktales.

In the Irish Rebellion of 1641, the English Army erected a fort at Belcoo which can be seen on the Down Survey maps of 1655. When the Irish surrendered at Cavan on 27 April 1653, paragraph 7 of the Articles of Surrender stated-"That Collonel Reily with the partie now with him on the west side of Loughern lay downe their armes, and deliver such forts in the islands, with all the amunicion and provision therein that is in his powre, at or before the 18 May next, at Crohan, and Collonel Hugh Me Guier's regiment to lay downe their armes the 18 May next, at 'Belcowe fort', in the county of Fermanagh, and all others of his partie included in these articles are to lay downe their armes in the severall counties where their quarters are, in such places as the Governors of the several counties shall apoynt." The fort was still in existence in 1700, as an entry in the Calendar of Treasury Books dated 1 June 1700 states there was "1 foot soldier at Belcoe who receives an allowance of £14 per annum in respect of fire and candle for the Barracks"

In Seamus Pender's "A Census of Ireland, Circa 1659", the village is called "Belcow".