Christianity is a monotheistic religion centered on Jesus of Nazareth, and on his life and teachings as presented in the New Testament. Christians believe Jesus to be the Messiah and thus refer to him as Jesus Christ. With an estimated 2.1 billion adherents in 2001, Christianity is the world's largest religion. It is the predominant religion in the Americas, Europe, Philippine Islands, Oceania, and large parts of Africa. It is also growing rapidly in Asia, particularly in China and South Korea, and Northern Africa.

Christianity began in the 1st century as a Jewish sect, and shares many religious texts with Judaism, specifically the Hebrew Bible, known to Christians as Old Testament (see Judeo-Christian). Like Judaism and Islam, Christianity is classified as an Abrahamic religion because of the centrality of Abraham in their shared traditions.

The name "Christian" (Greek Χριστιανός Strong's G5546) was first applied to the disciples in Antioch, as recorded in Acts 11:26. The earliest recorded use of the term Christianity (Greek Χριστιανισμός) is by Ignatius of Antioch.