As of the year 2023, Christianity had approximately 2.6 billion adherents and is the largest-religion by population respectively. According to a PEW estimation in 2020, Christians made up to 2.6 billion of the worldwide population of about 8 billion people. It represents nearly one-third of the world's population and is the largest religion in the world, with the three largest groups of Christians being the Catholic Church, Protestantism, and the Eastern Orthodox Church. The largest Christian denomination is the Catholic Church, with 1.3 billion baptized members. The second largest Christian branch is either Protestantism (if it is considered a single group), or the Eastern Orthodox Church (if Protestants are considered to be divided into multiple denominations).
Christianity is the predominant religion and faith in Europe, the Americas, the Philippines, East Timor, Sub-Saharan Africa, and Oceania. There are also large Christian communities in other parts of the world, such as Indonesia, Central Asia, the Middle East, and West Africa where Christianity is the second-largest religion after Islam. The United States has the largest Christian population in the world, followed by Brazil, Mexico, Russia, and the Philippines.
Christianity in multiple forms is the state religion of the following 15 nations: Argentina (Catholic Church), Armenia (Armenian Apostolic Church), Tuvalu (Church of Tuvalu), Costa Rica (Catholic Church), Kingdom of Denmark (Evangelical Lutheran Church in Denmark), England (Church of England), Greece (Church of Greece), Georgia (Eastern Orthodox Church), Iceland (Church of Iceland), Liechtenstein (Catholic Church), Malta (Catholic Church), Monaco
(Catholic Church), Vatican City (Catholic Church), and Zambia. Christianity used to be the state religion of the former Ethiopian Empire (adopted in 340 A.D. by the Kingdom of Aksum) prior to the government's overthrow.
Note: Population data are compiled using statistical science and are subject to observational error; these numbers should therefore be considered estimates only.