Drainage basin is a geographic term about rivers.It is also called catchment, catchment area, catchment basin, drainage area, river basin, and water basin.. It is an area of land. All water that falls on that land flows into one river. It can flow directly into the river or go through tributaries (smaller rivers that flow into the bigger river) first.

Category:Drainage basins. Wikimedia Commons has media related to Drainage basins. This category is for drainage basins. For endorheic (closed) basins and structural basins which may contain more than one drainage basin, see Category:Endorheic basins and Category:Depressions (geology). This category is about natural drainage.

Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic conditions that harm root growth), but many soils need artificial drainage to improve production or to manage water supplies.