马哈威利河（英语：Mahaweli River；僧伽罗语：මහවැලි ගඟ，意为大沙河；泰米尔语：மகாவலி ஆறு [mahawali gangai]）,是斯里兰卡最长河流，干流河长335 km（208 mi）。它也是该国最大河流，流域面积几占全国五分之一。

马哈威利河发源于斯里兰卡岛中南部的吉里加尔波塔山、托塔波拉山附近的霍顿平原。干流向北流至康提附近转向东流，至汉达甘纳瓦附近再转向北流，最终注入亭可马里南侧海湾。

该海湾因有多个海底峡谷，使得亭可马里港成为世界最佳的深水良港之一。

The Mahaweli River (Sinhalese:මහවැලි ගඟ Mahawaluka nadee, literally "Great Sandy River"; Tamil:மகாவலி ஆறு [mahawali gangai]), is a 335 km (208 mi) long river, ranking as the longest river in Sri Lanka. Its drainage basin is the largest in the country, and covers almost one-fifth of the total area of the island. The river reaches the Bay of Bengal on the southwestern side of Trincomalee Bay. The bay includes the first of a number submarine canyons, making Trincomalee one of the finest deep-sea harbors in the world. The river and its tributaries are dammed at several locations to allow irrigation in the dry zone, with almost 1,000 km (386 sq mi) of land irrigated. Production of hydroelectricity from six dams of the Mahaweli system supplies more than 40% of Sri Lanka's electricity needs. One of the many sources of the river is the Kotmale Oya.