Lake Mai-Ndombe is a large freshwater lake in Mai-Ndombe province in western Democratic Republic of the Congo. The lake is within the Tumba-Ngiri-Maindombe area, the largest Wetland of International Importance recognized by the Ramsar Convention in the world.

Tumba-Ngiri-Maindombe is the largest Wetland of International Importance in the world as recognized by the Ramsar Convention. The site covers an area of 65,696 square kilometres (25,365 sq mi) in the region around Lake Tumba in the western Congo Basin in the Democratic Republic of the Congo (DRC). This is more than twice the size of Belgium or Maryland.