John Smyth (1570 - c. August 28, 1612) was an early Baptist minister of England, and a defender of the principle of religious liberty. Many historians consider John Smyth as a founder of the modern Baptist denomination (see Baptist Origins).

Smyth was ordained as an Anglican priest in 1594 in England. Soon after his ordination, he broke with the Church of England and became a Separatist. In 1609, Smyth came to a belief in believer's baptism and opposed to infant baptism. Smyth baptized himself and his followers. He later rejected this baptism and sought baptism from the Mennonites. This brought about a separation between Smyth and a group led by Thomas Helwys. The churches that descended from Smyth and Helwys were of the General Baptist persuasion.