What Mythology speaks of transitions, shape-shifting, and/or gender role switching?

Question

Any and all mythology is good, but would especially appreciate any knowledge of Native American or Celtic lore.

I'm asking for specific stories, not general genre's. And yes, the bible is mythology, but I'm looking more for European indigenous myths rather than Middle Eastern.

Answer 1

Some Greek is the best.. The nymphs change into all things in nature and Tiresias was change from a man into a woman.

Nymphs, in Greek and Roman mythology, lesser divinities or spirits of nature, dwelling in groves and fountains, forests, meadows, streams, and the sea, represented as young and beautiful maidens, fond of music and dancing. The nymphs were distinguished according to the part of nature they personified, and included the Oceanids, or daughters of Oceanus, the ocean that flows around the earth; the Nereids, or daughters of the sea god Nereus, nymphs of the Mediterranean Sea; the Potameides, river nymphs; the Naiads, nymphs of springs and freshwater streams; the Oreads, nymphs of mountains and grottoes; and the Dryads, nymphs of the forests.

After Tiresias, separating a pair of snakes that he found copulating in the road, Tiresias was for a time transformed into a woman. Later, having become a man again, he was asked by Zeus and Hera, king and queen of the gods, to tell which sex had more pleasure in love. When he replied that woman had nine times as much pleasure as man, Hera, in anger, blinded him, but Zeus granted him long life.

Answer 2

Check the old and new testaments of Judaism and Christianity. They are all there to be found.

Ovid's Metamorphesis is a read.
The Hopi Katchina
The Danu of ancient Eire