Inishmacowney (Gaeilge: Inis Mhic Uaithne), also known as Horse Island, is an uninhabited island and townland in the River Fergus and Kildysart parish in County Clare, Ireland. The island has an area of 0.9698 km (239 acres) and consists of mainly grassland. The island has been uninhabited since 1976, but boasted a population of 44 in 1911.

Historical population

Year Pop. ±% 1841 142 —     1851 91 −35.9% 1861 103 +13.2% 1871 95 −7.8% 1881 75 −21.1% 1891 30 −60.0% 1901 37 +23.3% 1911 44 +18.9%	Year Pop. ±% 1926 41 −6.8% 1936 28 −31.7% 1946 24 −14.3% 1951 22 −8.3% 1956 20 −9.1% 1961 18 −10.0% 1966 15 −16.7% 1971 18 +20.0%	Year Pop. ±% 1979 2 −88.9% 1981 0 −100.0% 1986 0 0.00% 1991 0 0.00% 1996 0 0.00% 2002 0 0.00% 2006 0 0.00%
Source: Central Statistics Office. "CNA17: Population by Off Shore Island, Sex and Year". CSO.ie. Retrieved 12 October 2016.