John Calvin (; Middle French: Jean Cauvin; French: Jean Calvin [ kalv]; 10 July 1509 27 May 1564) was a French theologian, pastor, and reformer in Geneva during the Protestant Reformation. He was a principal figure in the development of the system of Christian theology later called Calvinism, including its doctrines of predestination and of God's absolute sovereignty in the salvation of the human soul from death and eternal damnation. Calvinist doctrines were influenced by and elaborated upon the Augustinian and other Christian traditions. Various Congregational, Reformed and Presbyterian churches, which look to Calvin as the chief expositor of their beliefs, have spread throughout the world.

Calvin was a tireless polemicist and apologetic writer who generated much controversy. He also exchanged cordial and supportive letters with many reformers, including Philipp Melanchthon and Heinrich Bullinger. In addition to his seminal Institutes of the Christian Religion, Calvin wrote commentaries on most books of the Bible, confessional documents, and various other theological treatises.

Calvin was originally trained as a humanist lawyer. He broke from the Roman Catholic Church around 1530. After religious tensions erupted in widespread deadly violence against Protestant Christians in France, Calvin fled to Basel, Switzerland, where in 1536 he published the first edition of the Institutes. In that same year, Calvin was recruited by Frenchman William Farel to join the Reformation in Geneva, where he regularly preached sermons throughout the week. However, the governing council of the city resisted the implementation of their ideas, and both men were expelled. At the invitation of Martin Bucer, Calvin proceeded to Strasbourg, where he became the minister of a church of French refugees. He continued to support the reform movement in Geneva, and in 1541 he was invited back to lead the church of the city.

Following his return, Calvin introduced new forms of church government and liturgy, despite opposition from several powerful families in the city who tried to curb his authority. During this period, Michael Servetus, a Spaniard regarded by both Roman Catholics and Protestants as having a heretical view of the Trinity, arrived in Geneva. He was denounced by Calvin and burned at the stake for heresy by the city council. Following an influx of supportive refugees and new elections to the city council, Calvin's opponents were forced out. Calvin spent his final years promoting the Reformation both in Geneva and throughout Europe.

Geneva ( jin-EE-və; officially French: Genève [ʒənɛv] (listen)) is the second-most populous city in Switzerland (after Zürich) and the most populous city of Romandy, the French-speaking part of Switzerland. Situated where the Rhône exits Lake Geneva, it is the capital of the Republic and Canton of Geneva.

The municipality (ville de Genève) has a population (as of December 2020) of 203,856, and the canton (essentially the city and its inner-ring suburbs) has 506,343 residents. In 2014, the compact agglomération du Grand Genève had 946,000 inhabitants in 212 communities in both Switzerland and France. Within Swiss territory, the commuter area named "Métropole lémanique" contains a population of 1.26 million. This area is essentially spread east from Geneva towards the Riviera area (Vevey, Montreux) and north-east towards Yverdon-les-Bains, in the neighbouring canton of Vaud.

Geneva is a global city, a financial centre, and a worldwide centre for diplomacy due to the presence of numerous international organizations, including the headquarters of many agencies of the United Nations and the Red Cross. Geneva hosts the highest number of international organizations in the world. It is also where the Geneva Conventions were signed, which chiefly concern the treatment of wartime non-combatants and prisoners of war. Together with, for instance, New York City (global headquarters of the UN), Basel (Bank for International Settlements), and Strasbourg (Council of Europe), Geneva is a city serving as the headquarters of one of the most important international organizations, without being the capital of a country.In 2021, Geneva was ranked as the world's ninth most important financial centre for competitiveness by the Global Financial Centres Index, fifth in Europe behind London, Zürich, Frankfurt and Luxembourg. In 2019, Geneva was ranked among the ten most liveable cities in the world by Mercer together with Zürich and Basel. The city has been referred to as the world's most compact metropolis and the "Peace Capital". In 2019, Mercer ranked Geneva as the thirteenth most expensive city in the world. In a UBS ranking of global cities in 2018, Geneva was ranked first for gross earnings, second most expensive, and fourth in purchasing power.