In Greek mythology, Demonice is the name of two women.
- Demonice a maiden of Ephesus. Brennus, king of the Gauls who was razing Asia Minor came to Ephesus and fell in love with Demonice. She promised to yield to him, and also to betray her country, if he would give her golden bracelets and the jewels of the Gaulish women. Brennus told his soldiers to throw into her lap the gold they were wearing, and she was buried alive.
- Demonice, daughter of Agenor and Epicaste, sister of Porthaon. She bore Ares four sons: Evenus, Molus, Pylus, and Thestius.