Portsmouth
- County:
- Scioto County
- County Seat:
- Yes
- Area (mi²):
- 10.729
- State:
- Ohio
Portsmouth is a city located in Scioto County, Ohio. Portsmouth has a 2026 population of 17,489. It is also the county seat of Scioto County. Portsmouth is currently declining at a rate of -0.63% annually and its population has decreased by -3.94% since the most recent census, which recorded a population of 18,207 in 2020.