Johannes Mensing (Mensingk) (1477–1547) was a German Dominican theologian and controversialist, an opponent of Martin Luther.
To prevent Lutheran doctrinal innovations from gaining a foothold in his province, Mensing entered into all the controversies.
He was forced to leave, and took up the invitation of the Princess Margaretha von Anhalt, who ruled during the minority of her sons; he went to Dessau to support her in her efforts against Protestants in her territory.
In 1534, he was elected provincial of his own province, but before the termination of his office Pope Paul III made him suffragan Bishop of Halberstadt.
In 1540 and 1541, he attended the theological conferences of Worms and Ratisbon, where with Johann Eck, the vice-chancellor of the University of Ingolstadt, and Pelargus, he took a leading part in the deliberations.