Presbyterianism is a branch of Protestant Christianity that adheres to the Calvinist theological tradition and whose congregations are organized according to a Presbyterian polity. Presbyterian theology typically emphasizes the sovereignty of God, the authority of the Scriptures, and the necessity of grace through faith in Christ. Presbyterianism originated primarily in Scotland. Scotland ensured Presbyterian "church government" in the Acts of Union in 1708 which created the kingdom of Great Britain. In fact, most Presbyterians found in England can trace a Scottish connection, and the Presbyterian denomination was also taken to North America mostly by Scots and Scots-Irish immigrants. The Presbyterian denominations in Scotland hold to the theology of Calvin and his immediate successors, although there is a range of theological views within contemporary Presbyterianism.
 
Modern Presbyterianism traces its institutional roots back to the Scottish Reformation. Local congregations are governed by Sessions made up of representatives of the congregation, a conciliar approach which is found at other levels of decision-making (Presbytery, Synod and General Assembly). Theoretically, there are no bishops in Presbyterianism; however, some groups in Eastern Europe, and in ecumenical groups, do have bishops. The office of elder is another distinctive mark of Presbyterianism: these are specially ordained non-clergy called ruling elders and ministers of Word and Sacrament called teaching elders who take part in local pastoral care and decision making at all levels. The office of deacon is geared toward the care of members, their families, and the surrounding community. In some congregations active elders and deacons serve a three-year term that is renewable for a second three-year term and then rotate off for at least a year. The offices of pastor, elder, and deacon all commence with ordination; once a person is ordained, he holds that title for the rest of his life. An individual may serve as both an elder and a deacon.
 
The roots of Presbyterianism lie in the European Reformation of the 16th century, with the example of John Calvin's Geneva being particularly influential. Most Reformed churches who trace their history back to Scotland are either Presbyterian or Congregationalist in government. In the twentieth century, some Presbyterians played an important role in the Ecumenical Movement, including the World Council of Churches. Many Presbyterian denominations have found ways of working together with other Reformed denominations and Christians of other traditions, especially in the World Communion of Reformed Churches. Some Presbyterian churches have entered into unions with other churches, such as Congregationalists, Lutherans, Anglicans, and Methodists.

Presbyterian denominations derive their name from the Greek word presbýteros (???????????), "elder." (Presbyterian church in Acts 14:23, 20:17, Titus 1:5).
 
The earliest Christian church consisted of Jews in the first century who had known Jesus Christ and heard his teachings. It gradually grew and spread from the Middle East to other parts of the world, though not without controversy and hardship among its supporters.
 
During the 4th century, after more than 300 years of repression and sometimes fierce persecution under various Roman emperors, the church became established as a political as well as a spiritual power under the Emperor Constantine. Theological and political disagreements, however, served to widen the rift between members of the eastern (Greek-speaking) and western (Latin-speaking) branches of the church. Eventually the western portions of Europe came under the religious and political authority of the Roman Catholic Church. Eastern Europe and parts of Asia came under the authority of the Eastern Orthodox Church.

In western Europe, the authority of the Roman Catholic Church remained largely unquestioned until the Renaissance in the 15th century. The invention of the printing press in Germany around 1440 made it possible for common people to have access to printed materials including the Bible. The public availability of the Bible encouraged private devotion away from the structure of the Roman Catholic Church. Printed materials also served to expose the populace to religious thinkers who had begun to question the authority and integrity of the Church. One such figure, Martin Luther, a German Augustinian friar and professor, enumerated this dissent in his 95 Theses. In 1517, Luther famously posted his grievances on a church door in Wittenberg, Germany. This moment is said to have marked the beginning of the Protestant Reformation, a theological movement intended to reform the Church. As the Catholic Church resisted the reformers, the Church split and different theological movements bore different denominations. Presbyterianism was especially influenced by the French/Swiss theologian, John Calvin, who is credited with the development of Reformed theology and the work of John Knox, a Scotsman who studied with Calvin in Geneva, Switzerland and brought his teachings back to Scotland. The Presbyterian church traces its ancestry back primarily to England and Scotland. In August 1560 the Scottish Parliament adopted the Protestant Confession of Faith as the creed of the Scottish Kingdom. In December of that year, the First Book of Discipline was published, outlining important doctrinal issues but also establishing regulations for church government, including the creation of ten ecclesiastical districts with pointed superintendents which later became known as presbyteries.
 
Among the early church fathers, it was noted that the offices of elder and bishop were identical, and were not differentiated until later, and that plurality of elders was the norm for church government.[citation needed] St. Jerome (347-420) "In Epistle Titus", vol. iv, said, "Elder is identical with bishop; and before the urging of the devil gave rise to factionalism in religion, so much that it was being said among the people, 'I am of Paul, I of Apollos, I of Cephas', the churches were governed by a joint council of elders. After it was... decreed throughout the world that one chosen from among the presbyters should be placed over the others." This observation was also made by Chrysostom (349-407) in "Homilia i, in Phil. i, 1" and Theodoret (393-457) in "Interpret ad. Phil. iii", 445.
 
Presbyterianism was first described in detail by Martin Bucer of Strasbourg, who believed that the early Christian church implemented presbyterian polity. The first modern implementation was by the Geneva church under the leadership of John Calvin in 1541.