Christianity has a long and continuous history in Lebanon. Biblical scriptures show that Peter and Paul evangelized the Phoenicians, leading to the dawn of the ancient Patriarchate of Antioch. As such, Christianity in Lebanon is as old as the Christian faith itself. Christianity spread slowly in Lebanon due to pagans who resisted conversion, but it ultimately spread throughout the country. Even after centuries of living under Muslim Empires, Christianity remains the dominant faith of the Mount Lebanon region and has substantial communities elsewhere.

The Maronite Catholics and the Druze founded modern Lebanon in the nineteenth century, through a governing and social system known as the "Maronite-Druze dualism" in the Mount Lebanon Mutasarrifate. Lebanon has the second highest proportion of Christians of any Middle Eastern country (after Cyprus), estimated to be between 37% and 43%; Egypt and Syria are next, at roughly 10%. Lebanese Christians constitute the majority of the Lebanese diaspora worldwide.

Before the Christian faith reached the territory of Lebanon, Jesus had traveled to its southern parts near Tyre where the scripture tells that he cured a possessed Canaanite child. Christianity in Lebanon is as old as gentile Christian faith itself. Early reports relate the possibility that Saint Peter himself was the one who evangelized the Phoenicians whom he affiliated to the ancient Patriarchate of Antioch. Paul also preached in Lebanon, having lingered with the early Christians in Tyre and Sidon. Even though Christianity was introduced to Lebanon after the first century AD, its spread was very slow, particularly in the mountainous areas where paganism was still unyielding.

The earliest indisputable tradition of Christianity in Lebanon can be traced back to Saint Maron in the 4th century AD, being of Greek/Eastern/Antiochian Orthodox origin and the founder of national and ecclesiastical Maronitism. Saint Maron adopted an ascetic and reclusive life on the banks of the Orontes river in the vicinity of Homs–Syria and founded a community of monks which began to preach the gospel in the surrounding areas. By faith, liturgy, rite, religious books and heritage, the Maronites were of Eastern origin. The Saint Maron Monastery was too close to Antioch to grant the monks their freedom and autonomy, which prompted Saint John Maron, the first Maronite patriarch-elect, to lead his monks into the Lebanese mountains to escape emperor Justinian II's persecution, finally settling in the Qadisha valley. Nevertheless, the influence of the Maronite establishment spread throughout the Lebanese mountains and became a considerable feudal force. The existence of the Maronites was largely ignored by the western world until the Crusades. In the 16th century, the Maronite Church adopted the catechism of the Catholic Church and reaffirmed its relationship with it. Moreover, Rome dispatched Franciscan, Dominican and later Jesuit missionaries to Lebanon to Latinise the Maronites.

The relationship between the Druze and Christians has been characterized by harmony and peaceful coexistence, with amicable relations between the two groups prevailing throughout history, with the exception of some periods, including 1860 Mount Lebanon civil war.

Due to their turbulent history, the Maronites formed a secluded identity in the mountains and valleys of Lebanon, led by the Maronite patriarch who voiced his opinion on contemporary issues. They identify themselves as a unique community whose religion and culture is distinct from the predominantly Muslim Arab world. The Maronites played a major part in the definition of and the creation of the state of Lebanon. The modern state of Greater Lebanon was established by France in 1920 after the instigation of ambitious Maronite leaders headed by patriarch Elias Peter Hoayek, who presided over delegations to France following World War I and requested the re-establishment of the entity of the Principality of Lebanon (1515AD–1840AD). With the creation of the state of Lebanon, Arabism was overcome by Lebanism, which emphasizes Lebanon's Mediterranean and Phoenician heritage. In the National Pact, an unwritten gentleman's agreement between the Maronite President Bshara el-Khoury and Sunni prime minister Riad as-Solh, the seats of presidency were distributed between the main Lebanese religious denominations. According to the pact, the President of the Lebanese republic shall always be a Maronite. Furthermore, the pact also states that Lebanon is a state with an "Arab face" (not an Arab identity).

In 2014, according to *وقائع إنتخابية عن لبنان، حسب لوائح الناخبين الرسمية الصادرة عن وزارة الداخلية اللبنانية لسنة ٢٠١٤*, Christians made up 36.66% of registered voters aged 21 and above: 19.97% Maronites, 7.69% Orthodox, 5.01% Melkites and 4.22% other Christian minorities. In 2022, based on the registered voters aged 21+ for the elections, Christian represented 37.46%: 19.94% Maronites, 7.82% Orthodox, 5.26% Melkite and 4.75% other Christian minorities. The overall proportions remained very stable between 2014 and 2022, with only slight increases in all groups.

Note that the following percentages are estimates only. As the last Lebanese census was conducted in 1932, it is difficult to have precise population estimates.