Saint Thais was a penitent woman of Egypt in the fourth century. While little is known of her life, she was a sinful woman converted by a monk, perhaps Paphnutius of Thebes, who then lived three years in a narrow cell in most profound penitence.

It is said that she was a courtesan, and the monk entered her chamber to convert her. She acknowledged belief in God, and the monk exhorted her to repentance. She burned all her worldly goods, and lived in an enclosed cell as a penance. After three years she was removed, and she died fifteen days later.