Though much of Welsh mythology has been lost, shapeshifting magic features several times in what remains.
Pwyll was transformed by Arawn into Arawn's own shape, and Arawn transformed himself into Pwyll's, so that they could trade places for a year and a day.
Llwyd ap Cil Coed transformed his wife and attendents into mice to attack a crop in revenge; when his wife is captured, he turned himself into three clergymen in succession to try to pay a ransom.
Math and Gwydion transform flowers into a woman named Blodeuwedd, and when she betrays her husband Lleu, who is transformed into an eagle, they transform her again, into a owl.
Gilfaethwy having committed rape, and Gwydion his brother having helped him, they were transformed into animals, for one year each, Gwydion into a stag, sow and wolf, and Gilfaethwy into a hind, boar and she-wolf. Each year, they had a child. Math turned the three young animals into boys.
Gwion, having accidentally taken some of wisdom potion that Ceridwen was brewing for her son, fled her through a succession of changes that she answered with changes of her own, ending with his being eaten, a grain of corn, by her as a hen. She became pregnant, and he was reborn in a new form, as Taliesin.
Irish mythology features less, though Aoife turned her stepchildren, the Children of Lir, into swans to be rid of them. This may reflect less use of the motif, or that different types of stories were preserved from Irish mythology, much of which has been lost.