A channel is a type of landform which has the outline path of flows most commonly the confine of a river, river delta or strait. Channels can be either natural or human-made. There is a difference between channel bed and banks.

Channel refers to a mountain slope where water begins to flow between identifiable banks. Channel heads are very often associated with colluvium, hollows and landslides.

Natural channel is formed by fluvial process and is found across the Earth. These are mostly formed by flowing water from the hydrological cycle, though can also be formed by other flows such as draw upon lava. Channels also describe the deeper course through a reef, sand bar, bay, or any shallow body of water. One example is the Columbia River, a river located in the US states of Washington and Oregon, and which empties into the Pacific Ocean in Astoria, Oregon.

The term channel has another meaning of strait which is defined as a relatively narrow body of water that connects two larger bodies of water. There are terms like strait, channel, sound, and passage are synonymous and usually interchangeable.

Extraterrestrial natural channels are found elsewhere in the Solar System than the Earth and the longest and widest of which are the outflow channels on Mars and the channels of Venus many of which are tens of kilometers wide. The exact formation of these large ancient channels is unknown although it is theorized that those on Mars may have been formed due to catastrophic flooding.