A polder is a low-lying tract of land that forms an artificial hydrological entity, enclosed by embankments known as dikes and requiring drainage by pumps to prevent the water table within it from rising too high. The best known examples are those polders that constitute areas of land reclaimed from a body of water, such as a lake or the sea, and are consequently below the surrounding water level.

Polders are most commonly found, though not exclusively so, in the Netherlands, the country they are frequently associated with. This also leads the expression used to describe Dutch decision making - the Polder Model.

See also:

• Zuiderzee Works
• IJsselmeer
• Land reclamation