This article critically examines the relationship between archaeology and myth within medieval archaeology. Recent decades have witnessed a surge of research examining pre-Christian ritual, belief and religion. Here, mythology, saga, placenames and folklore has become increasingly utilised to reconstruct the mentalities and cosmologies of societies from around medieval Europe. As a wider global phenomenon, however, this trend comes with pitfalls too often glossed over or occluded, and which it is argued here, scholarship must begin to address more systematically. This article examines these issues through the nexus of literature and landscape in early medieval Ireland. It begins with an overview of recent trends in cognate disciplines that have implications for archaeological accounts purporting to access religion, belief and wider cosmological frameworks. Subsequently, it proceeds through a series of case studies examining major landscapes: the Hill of Tara, Brú na Boinne (both Co. Meath), and Nenagh (Co. Tipperary), in the Republic of Ireland. Through this lens it is argued that far from being relics of pre-historic cult practices, many of the deities that populate these landscapes and respective mythological narratives would appear to have been consciously invented for political, allegorical and exegetical reasons during the medieval period. This creative process had a marked monumental dimension focusing on the 8th century AD, contemporary with the floruit of literature for which Ireland is so famous. As a consequence, it is suggested that there are specific imperatives for these contemporary medieval developments that preclude their use of literary sources for reconstructing non-Christian cosmologies. These conclusions have implications more broadly for how recent research trends in archaeology utilise documentary sources, placenames and saga literature to reconstruct ritual, belief and religion across medieval Europe.