内流盆地（Endorheic basin）是指一个其中没有任何水体与外界水体相连的区域。

一般情形下在地球上大部分陆地地区，各种降水均通过河流流入海洋，以完成水气循环。而在内流盆地中，降水完全通过蒸发或渗漏离开地表，不与外界水系相连。内流盆地中一般均具有内流湖，但该湖泊往往易于干涸，并且盐度很高。内流盆地中心往往蕴藏着大量矿产，但同时生态系统脆弱，容易崩溃于水体污染。

世界各大洲中，大洋洲的内流盆地占全洲面积64%以上，北美洲则只有10%。总体来说，不包括南极洲，世界陆地总面积中18%为内流盆地。

An endorheic basin (from the Ancient Greek: ἔνδον, éndon, "within" and ῥεῖν, rheîn, "to flow") is a closed drainage basin that retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but converges instead into lakes or swamps, permanent or seasonal, that equilibrate through evaporation. Such a basin may also be referred to as a closed or terminal basin or as an internal drainage system.