Water harvesting system, also called rainwater collection system or rainwater catchment system, technology that collects and stores rainwater for human use. Rainwater harvesting systems range from simple rain barrels to more elaborate structures with pumps, tanks, and purification system.

The nonpotable water can be used to irrigate landscaping, flush toilets, wash cars, or launder clothes, and it can even be purified for human consumption. With water scarcity a pressing problem for many densely populated regions, rainwater harvesting systems can supply households and businesses with water for use in dry seasons and lessen the demand on municipal systems.