The Glenmasan manuscript is a late 15th-century Gaelic vellum manuscript in the National Library of Scotland, Edinburgh, where it is catalogued as Adv.MS.72.2.3. It was previously held in the Advocates Library, Edinburgh, where it was classified as Gaelic MS LIII, and transferred to the National Library of Scotland on its foundation in 1925. The compilation contains Scottish Gaelic literary versions of tales of the Ulster Cycle, such as the Táin Bó Flidhais and Oided mac nUisnig (the latter a version of Longas mac nUislenn).