Niangua is a city in Webster County, Missouri, United States. The population was 405 at the 2010 census. Niangua is part of the Springfield, Missouri Metropolitan Statistical Area.
The first settlement was made at Niangua prior to the Civil War. A post office called Niangua has been in operation since 1870. The community takes its name from the nearby Niangua River.
Niangua is located at 37°23′20″N 92°49′52″W (37.388793, -92.831077). According to the United States Census Bureau, the city has a total area of 0.41 square miles (1.06 km2), all land.
Niangua lies three miles from Interstate 44 and five miles north of Marshfield.
As of the census of 2010, there were 405 people, 174 households, and 113 families living in the city. The population density was 987.8 inhabitants per square mile (381.4/km2). There were 200 housing units at an average density of 487.8 per square mile (188.3/km2).