The smallmouth bass (Micropterus dolomieu) is a species of freshwater fish in the sunfish family (Centrarchidae) of order Perciformes. It is the type species of its genus. One of the black basses, it is native to a wide area throughout eastern North America, encompassing the upper and middle Mississippi River basin, the Saint Lawrence River–Great Lakes system, and up into the Hudson Bay basin.

The smallmouth bass is marked by is a series of dark bars on the sides, and its upper jaw does not extend past the eye. It grows to a maximum recorded overall length of 69 cm (27 in), weighing up to 5.4 kg (12 lb). Specimens have been recorded living up to 26 years.

M. dolomieu is found only in clear water, preferring shallow, rocky-bottomed areas of lakes and rivers. Because it is relatively intolerant of any type of pollution, the smallmouth bass is a good natural indicator of a healthy environment. Carnivorous, its diet comprises crayfish, insects, and smaller fish, the young also feeding on zooplankton.

The female can lay up to 21,000 eggs which are guarded by the male in his nest.

One of the world's most popular gamefish, the smallmouth bass is stocked in rivers and lakes throughout the United States, and has been introduced in many countries, sometimes with adverse effects on native fish populations.