A swamp is an area of land that is permanently saturated or filled with water. Swamps are forested wetlands that are considered to be transition zones because both land and water play a role in creating this environment. They vary in size and are located all around the world. Swamps and marshes are specific types of wetlands that form along waterbodies containing rich, hydric soils. Marshes are wetlands that are continually or frequently flooded by nearby running bodies of water and are dominated by emergent soft-stem vegetation and herbaceous plants. Swamps are wetlands consisting of saturated soils or standing water and are dominated by water-tolerant woody vegetation such as shrubs, bushes, and trees.

Swamps are characterized by their saturated soils and slow-moving waters. The water that accumulates in swamps comes from a variety of sources including precipitation, groundwater, tides, and/or freshwater flooding. These hydrologic pathways all contribute to how energy and nutrients flow in and out of the ecosystem. As water flows through the swamp, nutrients, sediment, and pollutants are naturally filtered out.

Swamps can contain fresh water, seawater, or a mixture of both. Some swamps are permanent, while others come and go with fluctuations in the local water level. Swamps can often be found along rivers or the shores of large lakes. They vary in size and type, and are often classified by the types of trees that grow in them.

Swamps have traditionally held a very low property value compared to fields, prairies, or woodlands. They have a reputation for being unproductive land that cannot easily be utilized for human activities, other than hunting, trapping, or fishing. However, scientists now understand how valuable swamps can be. They help with flood control and water purification in addition to being a habitat for plants and animals. Some swamps can be restored by simply plugging drainage ditches or removing levees, while the solutions for others are more complex.