The Port of Colombo (known as Port of Kolomtota in the early 14th Century Kotte Kingdom) is the largest and busiest port in Sri Lanka as well as in South Asia. Located in Colombo, on the southwestern shores on the Kelani River, it serves as an important terminal in Asia due to its strategic location in the Indian Ocean. During the 1980s, the port underwent rapid modernization with the installation of Cranes, Gantries and other modern-day terminal requirements. Currently with a capacity of 4.1 million TEUs and a dredged depth of over 15 m (49 ft), the Colombo Harbour is one of the busiest ports in the world, and ranks among the top 35 ports. It is also one of the biggest artificial harbours in the world handling most of the country's foreign trade. It has an annual cargo tonnage of 30.9 million tons. The port is also the naval base for Sri Lanka Navy Western Fleet under the Commander Western Naval Area (COMWEST).[citation needed] The Port of Colombo is home to the second tallest building in South Asia and is the center for many commercial interests.

In 2008, the port commenced a large-scale expansion project at a cost of US$1.2 billion, which is expected dramatically increase the port's capacity and capabilities.[7] The project, which is headed by the Sri Lanka Ports Authority and built by the Hyundai Engineering & Construction Company, is expected to be completed by 11 April 2012.

The expansion project will consist of four new terminals that are 1200m in length and can accommodate 3 berths each, alongside a depth of 18 m (59 ft) (which can be deepened to 23 m (75 ft)). The channel width of the harbour is to be 560m and depth of 20m, with harbour basin depth of 18m and a 600m turning circle. Once completed, it will increase the annual container handling capacity from 4 million TEUs to approximately 12 million TEUs. It will also be able to accommodate larger container vessels, carrying around 12,000 TEUs. The first terminal was awarded to the China Merchants Holdings (International) - Aitken Spence consortium on 16 September 2010. The new terminal is planned to be operational by First Quarter 2013.