Gwyddno Garanhir is a figure steeped in Welsh legend, known as the ruler of the sunken land known as Cantre’r Gwaelod, situated off the coast of Wales. He is famed as the father of Elffin ap Gwyddno and the foster-father of the renowned Welsh poet Taliesin, as recounted in the late medieval tale known as Chwedl Taliesin (Ystoria Taliesin/Hanes Taliesin; “The Tale of Taliesin”).

According to legend, Gwyddno possessed a notable artifact: the basket of Gwyddno Garanhir, counted among the Thirteen Treasures of the Island of Britain. His realm, Cantre’r Gwaelod, was safeguarded from the sea by floodgates, with Caer Wyddno as its principal stronghold, believed to have stood northwest of present-day Aberystwyth. However, tragedy struck when the keeper of the floodgates, Seithenyn, neglected his duties due to inebriation, allowing the sea to engulf the land.

Though tales speak of Cantre’r Gwaelod’s submersion, Gwyddno is also credited with a landlocked portion of his kingdom to which he retreated. Variations in historical records and folklore link Gwyddno to different figures, with Gwyddno ap Clydno, the King of Meirionydd in the late 6th century, often suggested as a possible identification.

In Susan Cooper’s The Dark Is Rising series, Gwyddno reigns as the king of the Lost Lands depicted in Silver on the Tree.

His epithet, “Garanhir,” translates to “Long-Shanks,” “Crane-Legs,” or literally “Tall-Crane” in Welsh, adding a vivid imagery to his name.