John Calvin, a French Reformer, pastor, and theologian, is widely regarded as one of the greatest figures of the Protestant Reformation. Alongside Martin Luther and Huldrych Zwingli, Calvin played a pivotal role in shaping the movement. His most notable work, the Institutes of the Christian Religion, not only synthesized the diverse perspectives of Protestant sects but also became an anchor of Protestant theology.

Calvin's impact as a Reformer stemmed from his ability to systematize the Protestant vision by drawing upon the teachings of Luther, Zwingli, and other prominent figures.

Calvin, eventually, became the most influential figure in the Reformation movement, to the point where Protestants were often called Calvinists. The Separatists in England, who were originally Calvinists, objected to the Anglican Church and brought Calvinism to America, establishing Plymouth Colony in 1621. Consequently, Calvinism emerged as the leading Christian doctrine in New England, exerting considerable influence throughout the early years of the United States and even to this present day.