Sioux City is a city located in Woodbury and Plymouth counties in the state of Iowa, United States. It serves as the county seat of Woodbury County and functions as the primary city within the five-county Sioux City metropolitan area.
As of the 2024 estimate, the city has a population of approximately 86,875, making it the fourth-most populous city in Iowa. The surrounding region, which encompasses parts of northwestern Iowa, northeastern Nebraska, and southeastern South Dakota, is sometimes referred to collectively as Siouxland.