Newton County is a county located in the southwest portion of the U.S. state of Missouri. As of the 2020 census, the population was 58,648. Its county seat is Neosho. The county was organized in 1838 and is named in honor of John Newton, a hero who fought in the Revolutionary War.

Neosho 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 Statistical 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.