Protestantism is a movement within Christianity which owes its name to the 1529 Protestation at Speyer, but is originated to the year 1517 when Martin Luther began his dispute with the Catholic Church. This period of time, known as the Reformation, began a series of events resulting over the next 500 years in several newly denominated churches (listed below.) Some denominations were started by intentionally dividing themselves from the Roman Catholic Church, such as in the case of the English Reformation while others, such as with Luther's followers, were excommunicated after attempting reform. New denominations and organizations formed through further divisions within Protestant churches since the Reformation began. A denomination labeled "Protestant" subscribes to the fundamental Protestant principles—though not always—that is scripture alone, justification by faith alone, and the universal priesthood of believers.
The majority of Modern Protestants are members of Adventism, Anglicanism, Baptists, Calvinism (Reformed Protestantism), Lutheranism, Methodism and Pentecostalism. Nondenominational, Evangelical, charismatic, neo-charismatic, independent and other churches are on the rise, and constitute a significant part of Protestant Christianity.
This list gives only an overview, and certainly does not mention all of the Protestant denominations. The exact number of Protestant denominations, including the members of the denominations, is difficult to calculate and depends on definition. A group that fits the generally accepted definition of "Protestant" might not officially use the term. Therefore, it should be taken with caution. The most accepted figure among various authors and scholars includes around 900 million Protestant Christians.
Proto-Protestantism, or the Reformation prior to Luther refers to movements similar to the Protestant Reformation, but before 1517, when Martin Luther (1483–1546) is reputed to have nailed the Ninety-Five-Theses to the church door. Major early Reformers were Peter Waldo (c. 1140–c. 1205), John Wycliffe (1320s–1384), and Jan Hus (c. 1369–1415). It is not completely correct to call these groups Protestant due to the fact that some of them had nothing to do with the 1529 Protestation at Speyer which coined the term Protestant. In particular, the Utraquists were eventually accommodated as a separate Catholic rite by the papacy after a military attempt to end their movement failed. On the other hand, the surviving Waldensians ended up joining Reformed Protestantism, so it is not completely inaccurate to refer to their movement as Protestant.
Lutherans are a major branch of Protestantism, identifying with the theology of Martin Luther, a German friar, ecclesiastical reformer, and theologian. The whole of Lutheranism has about 70-90 million members.
Pietism was an influential movement in Lutheranism that combined its emphasis on Biblical doctrine with the Reformed emphasis on individual piety and living a vigorous Christian life. Pietists who separated from established Lutheran churches to form their own denominations are known as Radical Pietists. Although a movement in Lutheranism, influence on Anglicanism, in particular John Wesley, led to the spawning of Methodism.
The Anabaptists trace their origins to the Radical Reformation. Alternative to other early protestants, Anabaptists were seen as an early offshoot of Protestantism, although the view has been challenged by some Anabaptists. There are approximately 2.1 million Anabaptists as of 2015.
Schwarzenau Brethren Movement
Anglicanism has referred to itself as the via media between Catholicism and Protestantism. It considers itself to be both Catholic and Reformed. Although the use of the term "Protestant" to refer to Anglicans was once common, it is controversial today, with some rejecting the label and others accepting it. In Protestantism, Anglicans number over 85 million. Note Episcopal Churches are a type of Anglicanism.
United and uniting churches of the Anglican Communion
Other Anglican churches and Continuing Anglican movement
There are numerous churches following the Anglican tradition that are not in full communion with the Anglican Communion. Some churches split due to changes in the Book of Common Prayer and the ordination of women, forming Anglo-Catholic communities. A select few of these churches are recognized by certain individual provinces of the Anglican Communion.
Methodism emerged out the influence of Pietism within Anglicanism. Some 60-80 million Christians are Methodists.
The Holiness movement involves a set of beliefs and practices which emerged from 19th-century Methodism. As of 2015, churches of the movement had an estimated 12 million adherents.
Reformed Protestantism (Calvinism)
Reformed Protestantism, also known as the Reformed tradition, or more commonly Calvinism, is a movement which broke from the Catholic Church in the 16th century. There are from 55-100 million Christians identifying as Reformers.
Continental Reformed churches
Baptists emerged as the English Puritans were influenced by the Anabaptists, and along with Methodism, grew in size and influence after they sailed to the New World (the remaining Puritans who traveled to the New World were congregationalists). Note some Baptists fit strongly with the reformed tradition theologically but not denominationally. There are about 75-105 million Baptists.
In 2017, the Baptist World Alliance has 47 million members. 
Quakers (Society of Friends)
- Shakers (United Society of Believers in Christ's Second Appearing)
Irvingism and the Catholic Apostolic Church Movement
The Catholic Apostolic churches were born out of the 1830s revival started in London by the teachings of Edward Irving, and out of the resultant Catholic Apostolic Church Movement.
Campbellism and Millerism (Restorationist and Adventist)
Adventism was a result from Restorationism and the Restoration Movement, which sought to restore Christianity along the lines of what is known about the apostolic early church which Restorationists saw as the search for a more pure and more ancient form of the religion. This idea is also called Christian Primitivism. Following the Stone-Campbell Restoration Movement, William Miller preached the end of the world and the second coming of Christ in 1843/44. Some followers after the failed prediction became the Adventists, while other splinter groups eventually became apocalyptic restorationists. Many of the splinter groups did not subscribe to trinitarian theologies. Well known restorationist groups related in some way to Millerism include the Jehovah's Witnesses, Church of Jesus Christ of Latter Day Saints, World Mission Society Church of God, the Restored Church of God, and the Kingdom of Jesus Christ
Stone-Campbell Restoration Movement
Early Sabbath-Keeping Movements, predating Millerism
Millerism and comparable groups
Adventist Movement (Sunday observing)
Adventist Movement (Seventh Day Sabbath/Saturday observing)
Pentecostal and Charismatic
Pentecostal Holiness Movement
Other Charismatic movements
Uniting and United churches movement
These churches are the result of a merger between distinct denominational churches. Churches are listed here when their disparate heritage marks them as inappropriately listed in the particular categories above.
Free Evangelical Churches
Evangelical Christianity and interdenominational churches
Many churches are non-denominational. These churches have emerged into their own pseudo-denomination, with many similarities. Most of these churches have origins in a historic mainline Protestant denomination.
Evangelicalism is a transdenominational Protestant movement which maintains the belief that the essence of the Gospel consists of the doctrine of salvation by grace through faith in Jesus Christ's atonement.
Ethiopian Evangelicalism (P'ent'ay)
P'ent'ay (Ethiopian Evangelicalism) are a group of indigenous Protestant Eastern Christian Baptist, Lutheran, Pentecostal, and Mennonite denominations in full communion with each other and believe that Ethiopian Evangelicalism is the reformation of the current Orthodox Tewahido church as well as the restoration of it to the original Ethiopian Christianity. They uphold that in order for a person to be saved one has to accept Jesus as their Lord and Savior for the forgiveness of sins; and to receive Christ one must be "born again" (dagem meweled).
The Four Main Denominations:
- Misgana Church of Ethiopia
- Assembly of God
- Hiwot Berhan Church
- Emnet Kristos
- Light of Life Church
- Life.Church (formerly LifeChurch.tv, Edmond, Oklahoma)