Colombo has one of the world's largest manmade harbors. Most of Sri Lanka's foreign trade passes through the port. There are modern facilities for containerized cargo. Gem cutting is a Colombo specialty; other industries include food and tobacco processing, metal fabrication, engineering, and the manufacture of chemicals, textiles, glass, cement, leather goods, furniture, and jewelry. An oil refinery is on the city's outskirts. Colombo is also Sri Lanka's financial center; a major attempt was made during the 1980s to transform it into an offshore banking center.

The area was probably known to Greco-Roman, Arab, and Chinese traders more than 2,000 years ago as an open anchorage for oceangoing ships. Muslims settled there in the 8th cent. A.D. The Portuguese arrived in the 16th cent. and built a fort to protect their spice trade. The Dutch, also coveting this trade, gained control in the 17th cent. In 1796, Colombo passed to the British, who made it the capital of their crown colony of Ceylon in 1802. In the 1880s, Colombo replaced Galle as Ceylon's chief port and became a major refueling and supply center for merchant ships on the Europe–East Asia route. Colombo served as an Allied naval base in World War II and was made the capital of independent Ceylon in 1948. The Colombo Plan, an international program to aid the economic development of Asian nations, was launched at a conference there in 1950. Colombo was replaced as Sri Lanka's capital in 1982, when the new parliament building in Sri Jayewardenapura Kotte was inaugurated.

Two faculties of the Univ. of Sri Lanka, several colleges and research institutes, an observatory, a national museum, Independence Hall (1948), and numerous churches, mosques, and Buddhist and Hindu temples are in Colombo; on the outskirts are two Buddhist universities. About half the city's population is Sinhalese; there are also Tamils, Moors, and small European and Indian communities. Festering violence between the majority Sinhalese and minority Tamils continued to claim lives through the 1990s.