The Western Province (Sinhalese: බස්නාහිර පළාත Basnahira Palata; Tamil: மேல் மாகாணம் Mael Maakaanam) is one of the nine provinces of Sri Lanka, the first level administrative division of the country. The provinces have existed since the 19th century but did not have any legal status until 1987 when the 13th Amendment to the Constitution of Sri Lanka established provincial councils. The province is the most densely populated province in the country and is home to the legislative capital Sri Jayawardenepura Kotte as well to Colombo, the nation's administrative and business center.

Parts of present-day Western Province were part of the pre-colonial Kingdom of Kotte. The province then came under Portuguese, Dutch and British control. In 1815 the British gained control of the entire island of Ceylon. They divided the island into three ethnic based administrative structures: Low Country Sinhalese, Kandyan Sinhalese and Tamil. The Western Province was part of the Low Country Sinhalese administration. In 1833, in accordance with the recommendations of the Colebrooke-Cameron Commission, the ethnic based administrative structures were unified into a single administration divided into five geographic provinces. The districts of Chilaw, Colombo, Kalutara, Puttalam, Seven Korales (present day Kurunegala District), Three Korales, Four Korales and Lower Bulatgama (present day Kegalle District) formed the new Western Province. Chilaw District, Puttalam District and Seven Korales were transferred to the newly created North Western Province in 1845. Three Korales, Four Korales and Lower Bulatgama were transferred to the newly created Sabaragamuwa Province in 1889.

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