This volume presents the first edition of "Manawydan uab Llyr", the third branch of the Mabinogi, to be published in Welsh since Williams' groundbreaking volume "Pedeir Keinc y Mabinogi" was published seventy-five years ago. As well as the text of "Manawydan fab Llyr", the author also offers a detailed analysis of the text making the volume an ideal study companion. The edition includes the text from the "White Book of Rhydderch", various readings from the "Red Book of Hergest" and the fragment of text from "Peniarth 6" (omitted from previous editions). The volume includes a lengthy introduction which places the text in context and traces the roots of the characters encountered in this branch of the Mabinogi. Detailed notes and a full vocabulary are also included.