"Dermot and Grania's Bed" is a name attached to dolmens and portal tombs in counties from Clare to Donegal, each one said to be a resting place used by the eloping lovers Diarmuid and Gráinne as they fled the pursuing warrior Fionn Mac Cumhaill. The example near Ardagh in County Mayo is one such site, its prehistoric stones wrapped in the same enduring folklore that transformed so many ancient monuments into waypoints on a mythological love chase.

The structure belongs to the megalithic tradition, a broad category of stone monuments built across Atlantic Europe during the Neolithic and early Bronze Age periods. Portal tombs, the type most commonly given this lovers' name, consist of two tall upright stones forming an entrance, a back stone, and a large capstone tilted at an angle, creating a chamber that was used for burial. The association with Diarmuid and Gráinne is not ancient in any documented sense; it appears to reflect a later folk impulse to populate the landscape with characters from the Fenian cycle, one of the great bodies of Irish mythological narrative. The academic record of this particular site draws on the Survey of the Megalithic Tombs of Ireland, volume two, covering County Mayo, compiled by Ruaidhrí de Valera and Seán Ó Nualláin and published in 1964, which remains a foundational reference for the megalithic monuments of the west of Ireland.