Gampaha District (Sinhala: ගම්පහ දිස්ත්රික්කය gampaha distrikkaya, Tamil: கம்பஹா மாவட்டம் Kampahā Māvaṭṭam) is one of the 25 districts of Sri Lanka, the second level administrative division of the country. It is the second most populous district of Sri Lanka after Colombo District. The district is administered by a District Secretariat headed by a District Secretary (previously known as a Government Agent) appointed by the central government of Sri Lanka. The capital of the district is the town of Gampaha. Negombo however is the largest city and the commercial hub of Gampaha district. The district was carved out of the northern part of Colombo District in September 1978.
Gampaha District is located in the west of Sri Lanka and has an area of 1,387 square kilometres (536 sq mi). It is bounded by Kurunegala and Puttalam districts from north, Kegalle District from east, Colombo District from south and by the Indian Ocean from west. The borders of the district are the Ma Oya on the north, Kelani River on the south and 1,000 ft contour line on the east.
Gampaha District is divided into 13 Divisional Secretary's Division (DS Divisions), each headed by a Divisional Secretary (previously known as an Assistant Government Agent). The DS Divisions are further sub-divided into 1,177 Grama Niladhari Divisions (GN Divisions).