The Kelani River is Sri Lanka's 145-kilometer-long, fourth-longest river, flowing from the Sri Pada Mountain Range to the capital city of Colombo. This vital waterway supplies an impressive 80% of Colombo's drinking water and contributes significantly to the nation's hydroelectric power through its key tributaries, the Kehelgamu Oya and Maskeli Oya, which host several major reservoirs. Beyond providing essential resources, the river supports transport, fisheries, and sand mining, though intensive sand extraction contributes to challenges like annual flooding in Colombo and saline intrusion during dry seasons.

Culturally, the Kelani River holds deep significance for Sinhala Buddhists, being closely associated with revered sites such as Sri Pada Mountain and the Kelani Raja Maha Viharaya. An interesting historical note is that the Academy Award-winning film The Bridge on the River Kwai was partially filmed on the Kelani River near Kitulgala.