Caspar Schwenckfeld, German theologian and writer
Caspar (or Kaspar) Schwen(c)kfeld von Ossig (listen ) (1489 or 1490 – 10 December 1561) was a German theologian, writer, physician, naturalist, and preacher who became a Protestant Reformer and spiritualist. He was one of the earliest promoters of the Protestant Reformation in Silesia.

Schwenckfeld came to Reformation principles through Thomas Müntzer and Andreas Karlstadt. However, he developed his own principles and fell out with Martin Luther over the eucharistic controversy (1524). He had his own views on the sacraments - the Heavenly Flesh doctrine - developed in close association with his humanist colleague, Valentin Crautwald (1465–1545). His followers became a new sect (see Schwenckfelders), which was outlawed in Germany, but his ideas influenced Anabaptism, Pietism on mainland Europe, and Puritanism in England.

Many of his followers were persecuted in Europe and thus forced to either convert or flee. Because of this, there are Schwenkfelder Church congregations in countries such as the United States (which was then the Thirteen Colonies of Great Britain).