The Wood Duck or Carolina Duck (Aix sponsa) is a medium-sized perching duck. A typical adult is about 19 inches in length with an average wingspan of 29 inches. This is about three-quarters of the length of an adult Mallard. It shares its genus with the Asian Mandarin Duck.

The adult male has distinctive multi-colored iridescent plumage and red eyes. The female, less colorful, has a white eye-ring and a whitish throat. Both adults have crested heads. When swimming, wood ducks bob their head back and forth in a jerking motion, which makes them easy to spot.

Their breeding habitat is wooded swamps, shallow lakes, marshes or ponds in eastern North America, the west coast of the United States and western Mexico. They usually nest in cavities in trees close to water, although they will take advantage of nesting boxes in wetland locations if available. Their personality is shy and skittish.

Females typically lay between 9 and 14 eggs. However, if nesting boxes are placed too close together, females may lay eggs in the nests of their neighbors, which may lead to nests which may contain as many as 40 eggs and unsuccessful incubation, a behavior known as "nest dumping". They prefer nesting over water so the young have a soft landing, but will nest up to 150 yards (140 m) away from the shoreline. The day after they hatch, the young climb to the nest entrance and jump to the ground. The baby ducks can swim and find their own food by this time.

The birds are year-round residents in East Texas and other southern parts of their range, but the northern populations migrate south for the winter. They overwinter in the southern United States near the Atlantic coast. They are also popular, due to their attractive plumage, in waterfowl collections and as such are frequently recorded in Great Britain as escapes - populations have become temporarily established in Surrey in the past but are not considered to be self-sustaining in the fashion of the closely related Mandarin Duck. Given its native distribution the species is also a potential natural vagrant to Western Europe and there have been records in areas such as Cornwall and the Isles of Scilly which some observers consider may relate to wild birds; however, given the Wood Duck's popularity in captivity it would be extremely difficult to prove their provenance one way or another.

These birds feed by dabbling or walking on land. They mainly eat berries and seeds, but also insects, making them omnivores.

The male's call is a rising whistle; the female gives a whistled whoo-eek if startled.

The population of the Wood Duck was in serious decline at the beginning of the 20th century as a result of over-hunting and loss of suitable nesting sites. Changes in game laws and the construction of nesting boxes in suitable habitat resulted in this species' return to sustainable numbers.

Landowners as well as park and refuge managers can encourage Wood Ducks by building Wood Duck nest boxes near lakes, ponds, and streams. Fulda, Minnesota has adopted the wood duck as an unofficial mascot, and a large number of nest boxes can be found in the area.