Protestantism is a movement within Christianity that originated in the sixteenth-century Protestant Reformation. It is considered to be one of the four principal traditions within Christianity, together with Roman Catholicism, Anglicanism, and Orthodoxy. Protestantism is associated with the belief that the Bible (rather than church tradition or ecclesiastical interpretations of the Bible) is the final source of authority for Christians. Another salient feature of Protestant theology is its doctrine that salvation comes through faith alone, by the grace of God. The major sects of Christianity that belong to Protestantism include Lutherans, Presbyterians, Congregational Evangelists, Methodists, Baptists, Church of Christ, Holiness, Church of God, Pentecostals, and Charismatics. Cults that claim to be Christians (which include Jehovah's Witnesses, Mormons, and Seventh-Day Adventists, Oneness Pentecostals and Unitarians) also claim to be Protestant.

Most of the Christian believers that were taken in the Rapture in Left Behind: A Novel of the Earth's Last Days were believed to have been members of Protestant denominations. The New Hope Village Church that Irene Steele attended can be seen as a non-denominational Protestant church. Most Protestants, however, neither subscribe to the dispensationalist framework featured in the Left Behind books nor believe in the Rapture.

Basic doctrines of Protestantism

These may vary according to the sect that falls within the realm of Protestantism, but they include:

• Scripture alone has authority over a believer's walk with the Lord and is sufficient for guidance and comfort (refered to as Sola Scriptura).
• Scripture consists primarily of 66 books (no Deuterocanonicals)
• Salvation is through grace through faith alone (Sola Fide and Sola Gratia).
• Jesus alone is capable and sufficient enough to pay for all the sins of a believer (Sola Christus).