Chà Ân Uch'i (; 15th and 16th centuries) was a Taoist scholar during the Joseon dynasty of Korea. He is known by many as the most prominent " historical Taoist sorcerer" in Korean history, and a representative trickster from old Korean literature. His art name was Usa (), which means "featherman". Though he was a Taoist heretic, he studied Confucianism under Sà  Kyà Ângdà Âk.
According to the Complete Works from Azure Residence by Yi Deok-moo, when Chà Ân was very young, he went to a mountain temple to study in solitude. One day, the rice wine which was brewed at the temple vanished. The monks scolded Chà Ân, accusing him of drinking it. Chà Ân was aggrieved and upset, so he decided to hunt down the true culprit. He waited beside the wine jugs until twilight. At dusk, a nine-tailed fox came out from the forest and drank the wine until she was drunk. Chà Ân jumped out and tied her up with some rope. The fox offered him her grimoire if he would release her. Chà Ân accepted that and became a sorcerer through studying the fox's grimoire.
In another version of the story from one the Ilsamungo-version of the Chà Ân Uch'i chà Ân, young Chà Ân and a fox (who was shaped like a woman) loved each other. One day while they kissed each other, the fox's magical marble went into Chà Ân's mouth, and he swallowed it. Then she, abashed, ran away and he absorbed the marble's power, becoming a sorcerer.
According to the Unofficial History of the East Land, one day between 1522 and 1566, Yi Kil's farm (which is in today's Bupyeong District) was suffering from an epidemic, and Yi's serfs and neighbors were ill in bed. Then Chà Ân visited Yi and expelled a disease.
As he was Taoist heretic, if not anarchistic, there are some legends that Chà Ân opposed the Joseon dynastic government and the king. By one account, he ended up with being arrested and put to death by execution. Some time later, Ch'a Sik, who was Chà Ân's alumnus under Sà  Kyà Ângdà Âk, was visited by Chà Ân. Chà Ân borrowed Cha Anthology of Du Fu and went away. Cha had known nothing about Chà Ân's death, so he talked about this to other alumni. Surprised, they dig up Chà Ân's tomb and opened the coffin to find there was no body.