Inishmacsaint (Irish: Inis-maige-samh, meaning 'Island of the Sorrel Plain') is a monastery located on an island off the western shore of Lough Erne, County Fermanagh, Northern Ireland.

The site includes the ruins of a monastic church and an early stone cross, probably from the tenth and twelfth centuries.

Inishmacsaint was founded by St. Ninnidh, (d. 523/30).

The original monastic buildings were probably damaged or destroyed during the raids of the ninth or tenth centuries.

This article about a Northern Ireland building or structure is a stub.