A rain gutter also known as a "rain catcher", is a narrow channel, or trough, forming the component of a roof system which collects and diverts rainwater away from the roof edge.

The main purpose of a rain gutter is to protect a building's foundation by channeling water away from its base. The gutter also helps to reduce erosion, prevents leaks in basements and crawlspaces, protects painted or stained surfaces by reducing exposure to water,and provides a means to collect rainwater for later use.

Gutters are also very effective at keeping building egress areas clear of falling water. Going into a house entrance below water running straight off the roof in a heavy down pour is literally like taking a shower. This major reduction in moisture also helps to keep entrance surfaces dry and free of moss, slime, algae and other growths likely to cause slips.

Rain gutters can be made from a variety of materials such as cast iron, lead, zinc, galvanised steel, painted steel, copper, paintedaluminium, PVC (and other plastics), concrete, stone, and wood.

Water collected by a rain gutter is fed, usually via a downspout or "downpipe" (traditionally called a leader or conductor), from the roof edge to the base of the building where it is either discharged or collected.Water from rain gutters may be collected in arain barrel or a cistern.[citation needed]