A reforming theologian, Ursinus was born Breslau in 1534 and studied at Wittenberg from 1550 to 1557. He then moved to Geneva for further study and from there took a teaching post in his native city of Breslau. His doctrine of the Lord's Supper led to his dismissal from Breslau in 1559. But in 1561, thanks to his mentor Peter Martyr Vermigli, received an invitation from Elector Frederick III to come to Heidelberg as director of the theological academy.
It was at Heidelberg that with Caspar Olevianus he made his )most notable contribution to church life by drafting the Heidelberg Catechism (1563). He also undertook the defense of the Catechism against Lutheran objections.
From 1562 he added the professorship of dogmatics to his administrative duties and also prepared a new liturgy. Zanchius relieved him the burden of teaching in 1568, but Ursinus became involved in a difficult struggle to bring in a new discipline on the Genevan model (1570). The death of the electtor in 1577 opened the way for Lutheran influences. Ursinus, with Zanchius, move to Neustadt in 1578 and spent his last year there. In addition to his work on the Catechism, he also wrote an important treatise on the Lutheran Book of Concord and did much to promote Peter Martyr's Loci.