A scupper is an opening in the side walls of an open-air structure, for purposes of draining water. They are usually placed at or near ground level, and allow rain or liquids to flow off of the side of the open-air structure, instead of pooling within the walls.

There are three main kinds of scupper used:

1. Sailing ships would have scuppers at deck level, to allow for ocean or rainwater drainoff
2. Buildings with railed rooftops can construct scuppers to let rainwater drain off, instead of pooling within the railing of the roof. Scuppers can also be placed in a parapet, for the same purpose.
3. Scuppers placed a level slightly above ground level are known as "overflow" scuppers, limiting the level of the pooling water. These can be used practically or in decoration, as in a tiered fountain.