The Arnamagnæan Manuscript Collection (Danish: Den Arnamagnæanske Håndskriftsamling, Icelandic: Handritasafn Árna Magnússonar) derives its name from the Icelandic scholar and antiquarian Árni Magnússon (1663–1730) — Arnas Magnæus in Latinised form — who in addition to his duties as Secretary of the Royal Archives and Professor of Danish Antiquities at the University of Copenhagen, spent much of his life building up the collection of manuscripts that now bears his name.
In addition to the manuscripts proper, the collection contains about 14000 Icelandic, Norwegian (including Faroese, Shetland and Orcadian) and Danish charters, both originals and first-hand copies (apographa).
It further provided for the transfer from the Danish Royal Library (Det kongelige Bibliotek) of manuscripts belonging to the same categories as the manuscripts relinquished by the Arnamagnæan Institute, and contained a special clause relating to the transfer to Iceland of two manuscripts, the Codex Regius of the Poetic Edda and the vellum codex Flateyjarbók, both of which were in the Danish Royal Library (and would not have been deemed islandsk kultureje under the terms of the treaty).
The remainder of the collection comprises the Danish, Swedish, Norwegian and continental European manuscripts mentioned above.
In 2009 the Arnamagnæan Manuscript Collection was added to UNESCO's Memory of the World Register in recognition of its historical value.