Thomas Grantham (1633/34–1692) provided important leadership as an English nonconformist and General Baptist polemicist and messenger in the second half of the seventeenth century. Grantham was baptized around 1652 in the Baptist church at Boston, Lincolnshire, and became one of the most significant Baptist figures of the period, yet no major historical study of Grantham has appeared until now. In this first study of its kind, John Inscore Essick demonstrates that Grantham was instrumental in organizing and legitimizing the General Baptist movement in England, especially in the counties of Lincolnshire and Norfolk. Readers interested in Baptist history will find new information about Grantham’s life and ministry as well as a comprehensive introduction to his many writings and their context. The chapter on the office of Messenger builds on and expands the work of John F. V. Nicholson by examining Grantham’s role in consolidating the office of Messenger and establishing it as a distinctive third ministerial office among the General Baptists by the end of the seventeenth century. Those interested in nonconformity and dissent considered more broadly will discover that Grantham brought a sense of unity and legitimacy to the General Baptist movement, as he debated with spokesmen of the Church of England, other Dissenters, and even among his own kind. Still, as Inscore Essick shows in his treatment of a little-known collection of personal letters, Grantham could act intentionally and irenically with non-Baptist Christians, forging a deep friendship with a Church of England clergyman.