A water dispenser, known as water cooler (if used for cooling only), is a machine that dispenses and often also cools or heats up water with a refrigeration unit. It is commonly located near the restroom due to closer access to plumbing. A drain line is also provided from the water cooler into the sewer system.

Water dispensers come in a variety of form factors, ranging from wall-mounted to bottle filler water dispenser combination units, to bi-level units and other formats. They are generally broken up into two categories: point-of-use (POU) water dispensers and bottled water dispensers. POU water dispensers are connected to a water supply, while bottled water dispensers require delivery (or self-pick-up) of water in large bottles from vendors. Bottled water dispensers can be top-mounted or bottom-loaded, depending on the design of the model.

Bottled water dispensers typically use 11- or 22-liter (5- or 10-gallon) dispensers commonly found on top of the unit. Pressure coolers are a subcategory of water dispensers encompassing drinking water fountains and direct-piping water dispensers. Water cooler may also refer to a primitive device for keeping water cool.