What is the largest Protestant denomination in the United States?

Pinpointing the single largest Protestant group in the U.S. can be surprisingly complex. Unlike denominations with a single, hierarchical structure, the Baptist tradition is a vast family of independent churches and conventions. However, when the members of these various groups are counted together, they form the largest Protestant tradition in the country by a significant margin. The Southern Baptist Convention is by far the largest single Baptist body and the largest Protestant denomination in its own right.

This tradition has deep roots in the Protestant Reformation, particularly in the English Separatist movement. A core theological principle is "believer's baptism," the practice of baptizing only professing believers, typically by full immersion, rather than baptizing infants. This emphasis on individual faith and congregational autonomy—the idea that each local church is self-governing—resonated strongly in the American colonies and contributed to their widespread growth.

Today, the Baptist family in the United States is incredibly diverse, encompassing numerous conventions that vary in theology and practice, such as the historically Black National Baptist Convention. Their influence is most pronounced in the American South, a region often referred to as the "Bible Belt," where their churches are a central part of many communities. From social reformers like Martin Luther King Jr. to evangelists like Billy Graham, the tradition has played a significant role in shaping American culture and history.