Illaunloughan, a low-lying island in the Portmagee Channel roughly 120 metres from the mainland and a short distance west of Portmagee village, contains the remains of a monastic settlement whose graveyard was excavated across four seasons between 1992 and 1995. About seventy per cent of the island was examined in that time, making it one of the more thoroughly investigated small monastic islands in Ireland.

The name of the island is itself unresolved. Lochán may refer to a saint connected with the site, a possibility supported by the appearance of two saints of that name in the Martyrology of Oengus, compiled around AD 800, and by the existence of an ecclesiastical site called Killoughane at the eastern end of the Iveragh peninsula. Alternatively, the name may simply mean the island of the chaff. As for the burials, the excavators found extended adult graves arranged east to west, with heads to the west, clustered around a small drystone oratory, a type of simple stone-built prayer house characteristic of early Irish monasticism. Several graves predated the oratory itself. Most had stone-lined sides; some were lintelled, covered with flat slabs. A recurring detail was the placement of quartz pebbles with the bodies, and in two graves the pebbles were arranged with evident care around the edges of the slab bases. No personal objects were buried with the dead. The site also includes a leacht, a low rectangular stone monument used for commemorative prayer, and a gable shrine associated with what appears to have been a reliquary, a structure for housing the remains of a venerated person. Later medieval burials, notably concentrated to the west of the oratory, respected the space occupied by this shrine and its mound, avoiding it entirely. Among the later burials, many of the adult dead were women, a shift from the earlier monastic pattern. One burial at the west side of the oratory contained six silver pennies of Edward I and Edward III, deposited sometime after 1351. In the post-medieval period the island appears to have served as a ceallúnach, a burial ground for unbaptised infants, a practice once widespread across Ireland and associated with the belief that such children could not be interred in consecrated ground.