Beirut is the capital and largest city of Lebanon with a population of over 2.1 million as of 2007. The population of Beirut holds 75 percent of the urban population of Lebanon. Located on a peninsula at the midpoint of Lebanon's coastline with the Mediterranean Sea, Beirut serves as the country's largest and main seaport and also forms the Beirut Metropolitan Area, which consists of the city and its suburbs. The first mention of this metropolis is found in the ancient Egyptian Tell el Amarna letters, dating to the 14th century BCE, and the city has been continuously inhabited since.

There are wide-ranging estimates of Beirut's population from as low as 938,940 people to as high as 2,012,000. No population census has been taken in Lebanon since 1932. Best estimates on religious groups suggest: Muslim 59.7 percent (Shia, Sunni, Druze, Isma'ilite, Alawite or Nusayri), Christian 39 percent (Maronite Catholic, Greek Orthodox, Melkite Catholic, Armenian Orthodox, Syrian Catholic, Armenian Catholic, Syrian Orthodox, Roman Catholic, Chaldean, Assyrian, Copt, Protestant); other 10.3 percent.

Beirut is the most religiously diverse city of the Middle East with Christians, and Muslims both having a significant presence. Lebanon’s President is always a Christian (Maronite Christian), the Prime Minister is always a Sunni Muslim, and the Speaker of the Parliament is always a Shiite Muslim. Family matters such as marriage, divorce and inheritance are still handled by the religious authorities representing a person's faith. Calls for civil marriage are unanimously rejected by the religious authorities but civil marriages held in another country are recognized by Lebanese civil authorities. Until the mid-20th century, Beirut was also home to a Jewish community, in the Wadi Abu Jamil neighborhood.

Before the civil war broke out in 1975, neighborhoods of Beirut were fairly heterogeneous, but they have become largely segregated by religion since the conflict. East Beirut is characterized by a largely Christian population with a small Sunni Muslim minority.

Meanwhile, West Beirut is categorized by a Muslim majority, primarily Sunni, with small communities of Shiites, Druze, and Christians. Since the end of the civil war in 1990, East and West Beirut have begun to see an increase in Sunni Muslims and Christians moving into each half. Beirut's southern suburbs are largely populated by Shiite Muslims, while Beirut's Eastern suburbs are largely Christian. Northern Beirut has had and continues to have a large Lebanese Protestant community since the 19th century.

Beirut is Lebanon's seat of government and plays a central role in the Lebanese economy with its city center-, Hamra-, Verdun-, and Ashrafieh-based corporate firms and banks. The city is the focal point of the region's cultural life, renowned for its press, theatres, cultural activities, and nightlife.

By the second half of the 19th century, Beirut was in the process of developing close commercial and political ties with European imperial powers, France in particular. European interests in Lebanese silk and other export products transformed the city into a major port and commercial center. Meanwhile, Ottoman power in the region continued to decline. Sectarian and religious conflicts, power vacuums, and changes in the political dynamics of the region culminated in the 1860 Lebanon conflict. Beirut became a destination for Maronite Christian refugees fleeing from the worst areas of the fighting on Mount Lebanon and in Damascus. This influx altered the ethnic composition of Beirut, sowing the of future ethnic and religious troubles there and in greater Lebanon. Beirut was able to prosper as a result of European intervention and a general realization among the city's residents that commerce, trade, and prosperity depended on domestic stability.

In 1888, Beirut was made capital of a vilayet, or “province,” in Syria. By this time, Beirut had grown to be a cosmopolitan city with close links to Europe and the United States. Beirut also became a center of missionary activity that spawned impressive educational institutions, such as the American University of Beirut. French influence in the area soon exceeded that of any other European power. In 1911, the population mix was reported in the Encyclopedia Britannica as Muslims, 36,000; Christians, 77,000; Jews, 2,500; Druze, 400; foreigners, 4,100.

After the collapse of the Ottoman Empire following World War I, Beirut, along with the rest of Lebanon, was placed under the French Mandate. After Lebanon achieved independence in 1943, Beirut became its capital city. It remained an intellectual capital of the Arab world and quickly became a financial center for much of the Arab world and a major tourist destination.

This era of relative prosperity ended in 1975 when the Lebanese Civil War broke out. During most of the war, Beirut was divided between the Muslim west and the Christian east. The downtown area, previously the home of much of the city's commercial and cultural activities, became a no-man's land known as the "Green Line". Many inhabitants fled to other countries. Thousands of others were killed throughout the war, and much of the city was devastated. A particularly destructive period was the 1982 Israeli invasion, during which most of West Beirut was under siege by Israeli troops. Subsequently, southern Lebanon was occupied by the Israeli Defense Force until 2000 when Israel unilaterally withdrew. Simultaneously, Syria maintained a military force of 3,000 troops.

Since the end of the war in 1990, the people of Lebanon have been rebuilding Beirut. During the 2006 Israeli-Lebanese war, southern Beirut, home to most of the city’s Shia population, came under heavy bombardment, and much of Beirut’s infrastructure was destroyed. Reconstruction of downtown Beirut has been largely driven by Solidere, a development company established in 1994 by the late Rafik Hariri.

The 2005 assassination of former Lebanese Prime Minister Rafik Hariri near the Saint George Bay in Beirut shook the entire country. A month after the death of Hariri, approximately one million people gathered in Beirut for an opposition rally against Syrian presence that came to be known as the Cedar Revolution — the largest rally in Lebanon’s history at that time. The last Syrian troops withdrew from Beirut on 26 April 2005. The two countries established diplomatic relations on 15 October 2008.

In June 2009, Lebanon held national elections for Parliament and in November, it formed a national unity government. The new government includes Hezbollah, which heads the March 8 Alliance. The March 14 Alliance’s leader, Saad Hariri is Prime Minister, and the Independent candidate Michel Suleiman is President.