A Welsh goddess mentioned in the old Welsh stories now incorporated into the Mabinogion. She is the daughter of Don and the sister of Gwydion, the bard and magician.
Her name means the silver wheel (or queen of the wheel), which could be interpreted as the moon, suggesting that she is a goddess of the full moon, and the mother aspect of the triple goddess. Other researchers suggest that the name silver wheel is a reference to a spiders web, and that she may be have been seen as a spider goddess. This also attributes her as a weaver goddess, a very important role that links her with time, the cycle of life and other important Celtic goddesses.
She is principally mentioned in the story of Math, Son of Mathanwy. She applies for the post of foot holder to Math, but first she has to pass an initiatory test of virginity by stepping over Math’s wand. She instantly gives birth to two children, Dylan and Llew Llaw Gyffes.
From the overtones of the story it seems that her impregnation is the result of an affair with her brother. In any event Gwydion takes care of Llew, and brings him up as his own. Arianrhod puts a geise upon Llew by refusing to name him, refusing him arms, and denying him a mortal wife. These difficulties are overcome with the magic and wiles of Gwydion, Llew winning his name and arms from his mother, and taking Blodeuwedd the flower maiden (who is created for him by Math) as his wife.
It seems that Arianrhod was also associated with the Corona Borealis, which was named Caer Arianrhod by the Welsh, so she may also have been seen as a star goddess. The Greek goddess Araidne was also associated with that part of the sky and the two seem to share characteristics, phonetically and in attributes (the spider aspect), they may be linked in some way.
Arianrhod lived on a fortified Island in a tower called Caer Sidi situated in the Northern reaches of the realm, which served as an initiatory place for poets and souls who were about to be reborn.