Newtonsville is an unincorporated community and former village in Clermont County, Ohio, United States. The population was 392 at the 2010 census. In 2019, residents voted to dissolve the village.
Newtonsville was platted on March 30, 1838, by Stephen Whitaker and Cornelius Washburn. A post office called Newtonsville has been in operation since 1847. In the 19th century, the village was home to a gristmill and chair factory. The village gradually lost business after World War I.
In 2016, the Ohio State Auditor placed the village in a state of fiscal caution due to poor bookkeeping. Despite levying a one-percent income tax, Newtonsville ran a deficit of $112,000 by 2019, prompting the auditor to declare a state of fiscal emergency in the village. On November 5, 2019, residents passed an initiative to dissolve the village and return it to Wayne Township