Lakes and tanks in the metropolitan area of Greater Bangalore and the district of Bangalore Urban are reservoirs of varying sizes constructed over a number of centuries by various empires and dynasties for rainwater harvesting. Historically, these reservoirs were primarily either irrigation tanks or for the water supply, with secondary uses such as bathing and washing. The need for creating and sustaining these man-made dammed freshwater reservoirs was created by the absence of a major river nearby coupled with a growing settlement. As Bangalore grew from a small settlement into a city, both of the primary historical uses of the tanks changed. Agricultural land witnessed urbanization and alternate sources of water were provisioned, such as through borewells, piped reservoir water and later river water from further away.

An irrigation tank or tank is an artificial reservoir of any size. In countries like Sri Lanka and India they are part of historic methods of harvesting and preserving rainwater, critical in regions without perennial water resources. A tank is often an earthen bund constructed across a long slope to collect and store surface water from the above catchment and by taking advantage of local topography. The water would be used primarily for agriculture and drinking water, but also for bathing and rituals. The word tank is the English language substitute for several vernacular terms.