The Askew Codex (a.k.a. Codex Askewianus) is a manuscript of parchment in quarto size, or 21 x 16,5 cm, held by the British Library (BL Additional MS 5114), that contains Coptic translations of the Gnostic Pistis Sophia and parts of what G. R. S. Mead referred to as "extracts from The Books of the Savior."
The codex was purchased from the heirs of Dr. Anthony Askew by the British Museum (now the British Library) in 1785. Its origin is most probably Egypt, but it is not known where it was found or how it ended up in England. The codex contains 178 leaves or 356 pages, and is in excellent condition, with the exception of two leaves (pp. 337–344), which are missing. The complete manuscript was written by two different hands. Both hands used different inks, different page numberings and a different way to mark corrections. Both writers seem to be of the same period.
Until the discovery of the Nag Hammadi library in 1945, the Askew Codex was one of three surviving codices containing full copies of all of the gnostic writings that have survived until recent times; the other two are the Bruce Codex and the Berlin Codex.