Zacharius Ursinus (July 18, 1534 - 1583), German theologian, and one of the authors of the Heidelberg Catechism.

He was born at Breslau, and became a disciple of Melanchthon at Wittenberg. He afterwards studied divinity at Geneva under Calvin, and Hebrew at Paris under Jean Mercier .

In 1561 he was appointed professor in the Collegium Sapientiae at Heidelberg, where in 1563 at the instance of the elector-palatine, Frederick III , he drew up the Catechism in co-operation with Caspar Olevianus . The death of the elector in 1576 led to the removal of Ursinus, who occupied a professorial chair at Neustadt an der Haardt from 1578 until his death in 1583.

His Works were published in 1587-89, and a more complete edition by his son and two of his pupils, Pareus and Reuterus, in 1612.