Peniarth 6 is a medieval Welsh manuscript. It is part of the collection of Peniarth Manuscripts, named for Peniarth Mansion in Meirionnydd, south Gwynedd, where they were kept for many years.

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Among the texts are parts of the Four Branches of the Mabinogi, the oldest prose stories existing in British literature, and a version of Gereint and Enid.^[1][2] It dates to the period circa 1225-1275. Peniarth 6 is kept in the National Library of Wales, Aberystwyth.