Neosho (; originally Siouan pronunciation: [niˈoʒo] or Siouan pronunciation: [niˈoʒu]) is the most populous city in Newton County, Missouri, United States, which it serves as the county seat. With a population of 12,590 as of the 2020 census, the city is a part of the Joplin, Missouri Metropolitan Area, a region with an estimated 176,849 (2011) residents. Neosho lies on the western edge of the Ozarks, in the far southwest of the state.

The name "Neosho" is of Osage derivation from "Ne-u-zhu", meaning "clear, cold water", "many waters", or "the meeting of waters", which refers to local freshwater springs. The springs attracted varying cultures of Native American inhabitants for thousands of years. The Osage Nation had long occupied the territory at the time of European contact.

Like the Osage, European-American settlers were also attracted to the springs, and founded the community of Neosho in 1833. It was incorporated as a municipal government in 1878. Nicknamed "City of Springs", Neosho has long served as an agricultural center. Since 1888, it has been the site of the Neosho National Fish Hatchery, the oldest in the National Fish Hatchery System.

It is known locally as the "Gateway to the Ozarks". Since 1957, it has also been identified as "the Flower Box City".