Codex Regius (Latin: Cōdex Rēgius, "(The) Royal Book"; Icelandic: Konungsbók) or GKS 2365 4º is an Icelandic codex in which many Old Norse poems are preserved. It is made up of 45 vellum leaves, thought to have been written in the 1270s. It originally contained a further 8 leaves, which are now missing. It is the sole source for most of the poems it contains. In scholarly texts, this manuscript is commonly abbreviated as [R] for Codex Regius, or as [K] for Konungsbók.
Nothing was known of its whereabouts until 1643 when it came into the possession of Brynjólfur Sveinsson, then Bishop of Skálholt, who sent it as a present to King Frederick III of Denmark in 1662, hence the name. It was then kept in the Royal Library in Copenhagen until April 21, 1971, when it was brought back to Reykjavík and is now kept in the Árni Magnússon Institute for Icelandic Studies. Since air travel was not to be entirely trusted at the time with such precious cargo, it was transported by ship, accompanied by a military escort.
Codex Regius designated by siglum Le or 019 (in the Gregory-Aland numbering), ε 56 (von Soden), is a Greek uncial manuscript of the New Testament, dated paleographically to the 8th century. The manuscript is lacunose. It has marginalia.
The codex contains 257 thick parchment leaves (23.5 cm by 17 cm), with an almost complete text of the four Gospels. The codex contains five lacunae (Matt 4:22-5:14, 28:17-20, Mark 10:16-30, 15:2-20, John 21:15-25).
The text is written in two columns per page, 25 lines per page, in large, not round uncial letters. It has breathings (Spiritus asper, Spiritus lenis), and accents often added wrongly. It is carelessly written by an ignorant scribe. The letter phi is enormously large, the letter alpha presents the last stage of the uncial script.
The text is divided according to the κεφαλαια (chapters), whose numbers are given at the margin, and their τιτλοι (titles) at the top of the pages. It contains also the tables of the κεφαλαια (tables of contents) before each Gospel. There is also another division according to the Ammonian sections, with references to the Eusebian Canons at the margin. It contains lectionary markings at the margin (for liturgical reading).