Mudflats, or otherwise known as tidal flats, are coastal wetlands that form when mud is left behind by tides or rivers. They’re found in sheltered regions such as bayous, lagoons, estuaries, and bays. Mudflats might be seen geologically as exposed layers of bay mud, a result from :

- the deposition of estuarine silts
- marine animal detritus
- clays
The majority of the sediment in a mudflat is within the intertidal zone, therefore the flat is submerged and exposed about twice per day.

In the past, tidal flats were thought to be unhealthy, economically insignificant areas and were frequently scoured and developed into agricultural land. Several particularly shallow mudflat regions, like the Wadden Sea, for example, are now accepted among those practicing the sport of mudflat hiking.