Niels Hemmingsen (Nicolaus Hemmingius) (1513 in Taagerup – 1600 in Roskilde) was a Danish Lutheran theologian. He studied at the University of Wittenberg 1537 to 1542 under Melanchthon. Returning to Denmark, he became a prolific author of works in Latin. In 1574 he published Syntagma institutionum christianarum, but was obliged to retract it in 1576 following pressure from Augustus I of Saxony to suppress Crypto-Calvinism.
In 1575 he published Admonito de superstitionibus magicus vitandis, a warning against practicing witchcraft. This was an important text on demonology and witchcraft in the 16th Century. He used a wide definition of witchcraft, including not only harmful activities, but all superstitious and magical behavior. Not all witches had pacts with the devil. He wrote that most of the Devil's power came through illusions and that witches only did physically impossible things in dreams, like flying on brooms. Similarly, he found drowning tests unreliable since they relied on superstition that the Devil could manipulate.