Dupo is a village in St. Clair County, Illinois, United States. The population was 4,138 at the 2010 census, an increase from 3,933 in 2000. The village was settled in about 1750 and was incorporated in 1876. Its name is derived from Common Fields of Prairie du Pont (French: Bridge Prairie).
Dupo is located at 38°30′57″N 90°12′29″W (38.515702, -90.207992). It is located in the American Bottom floodplain of the Mississippi River.
According to the 2010 census, Dupo has a total area of 4.42 square miles (11.45 km2), all land.
Dupo had its start ca. 1905 when the railroad was extended to that point. The name is an abbreviation of DuPont.
In 2010 there were 4,138 people, 1,650 households, and 1,142 families residing in the village.