Baptists are one of the largest Protestant Free Church denominations. At the turn of the 21st century, there were about 43 million Baptists worldwide with about 33 million of those in the United States and 216,000 in Britain.

There are over 850,000 Baptists in South America and 230,000 in Central America and the Caribbean.

As indicated by their name, the primary Baptist distinctive is their practice of believer's baptism and corresponding rejection of infant baptism. Most Baptists are evangelical in doctrine, but Baptist beliefs can vary due to the congregational governance system that gives autonomy to individual local Baptist churches. Historically, Baptists have played a key role in encouraging religious freedom and separation of church and state.

In the United States, the two largest Baptist organizations are the Southern Baptist Churches (SBC) and American Baptist Churches (ABC), with the former being the more conservative branch. Notable Baptists have included Martin Luther King, Jr., Charles Spurgeon, John Bunyan and Billy Graham.

Many Baptists trace their denomination's origins to the early church, a period when the church consisted of committed believers who were baptized upon confession of faith as adults. Baptist beginnings have also been traced to medieval sects who protested against prevailing baptismal theory and practice, and to the Anabaptists of the Continental Reformation, especially in Zurich.

The Anabaptists (spiritual ancestors of the Mennonites, Amish, and Hutterites) share emphasized believer's baptism and religious freedom and were probably influential in the development of Baptist characteristics. However, some Anabaptists differed from the Baptists on many other issues such as pacifism and the communal sharing of material goods.

The origins of the Baptists are most commonly traced to John Smyth and the Separatists. In 1609, John Smyth, led a group of separatists to the Netherlands to start the General Baptist Church with an Arminian theology. In 1616, Henry Jacob led a group of Puritans in England with a Calvinist theology to form a congregational church that would eventually become the Particular Baptists in 1638 under John Spilsbury. Both groups had members who sailed to America as pilgrims to avoid religious persecution in England and Europe and who started Baptist churches in the early colonies. The Particular and General Baptists would disagree over Arminianism and Calvinism until the formation of the Baptist Union of Great Britain in the 1800s under Andrew Fuller and William Carey for the purpose of missions.

Baptist Churches were established in the American colonies from the mid-17th century. In 1639, Roger Williams founded a church on Baptist principles in Providence, Rhode Island, and this is usually regarded as the beginning of American Baptist history. Also established in the 17th century was a small group known as the Seventh Day Baptists, who required rest and worship on Saturday based on the fourth commandment.

In the 18th century, many of the General Baptist Churches in England were influenced by the Unitarians and ultimately ceased to insist on believer's baptism. However, Dan Taylor (1738-1816) formed a "New Connection" in 1770 that maintained Baptist principles and later united with the Baptist mainstream. The Baptist Missionary Society was founded by Particular Baptists in 1792, which would have a profound impact on the future of the Baptists. The Baptist revival in England inspired the Baptist Churches of America, leading to widespread missionary zeal and growth of the movement across America as the frontier extended. The Baptists became the largest religious group in many of the southern states; today, two-thirds of the members of Black Churches of the USA are Baptists.

In the 19th century, Baptist churches continued their rapid growth, and from their ranks came such great preachers as Charles Spurgeon, Robert Hall, Alexander Maclaren and John Clifford. In Britain, the Baptist Union was formed in 1813. Notable in its development was J.H. Shakespeare, who was secretary for over 25 years (1898-1924). The Baptist movement in Scotland was furthered by Archibald McLean (1733-1812), who strongly emphasized emulating the New Testament pattern in doctrine and practice. The "Scotch Baptists" were one of the sources of the Disciples of Christ movement.

In 1834, a Baptist church was formed in Hamburg under J.C. Oncken, and from there came an extensive Baptist movement in contentiental Europe and among Slavic-speaking people. Baptists were persecuted by Tsarist Russia and suffered from the restrictions on religious freedom under the Soviet regime, but their numbers have grown significantly in recent years (to about 548,000 in 1988). Baptists are the largest Protestant denomination in the countries of the former USSR.

In the 20th century, Baptist missionaries have established churches throughout Asia, Africa and South America. In 1905, the Baptist World Alliance was formed for the purpose of international Baptist cooperation. Its headquarters is in McLean, Virginia.