A bayou is a slow-moving creek or a swampy section of a river or a lake. Bayous are often associated with the southeastern part of the United States, especially the state of Louisiana.

Bayous are usually shallow and sometimes surrounded by trees and bushes. They can be freshwater, saltwater, or a combination of both. This combination is called "brackish water."

The plants and water of a bayou are home to hundreds of creatures: fish, shrimp, birds, even alligators.

People have been living in bayous for more than a thousand years. Native Americans known as Choctaws may have been the first people to live in and around Louisiana bayous. Cajun and Creole cultures, both native to Louisiana, are also associated with bayous.

Bayou Bartholomew is the longest bayou in the world and is located in the U.S. states of Arkansas and Louisiana. It is about 603 kilometers (375 miles) long and contains more than 100 different species of fish. Before railroad lines were constructed in the late 1800s, Bayou Bartholomew was an important waterway for transportation.