Ada
- County:
- Hardin County
- County Seat:
- No
- Area (mi²):
- 2.134
- State:
- Ohio
Ada is a village located in Hardin County, Ohio. Ada has a 2026 population of 5,293. Ada is currently declining at a rate of 0% annually and its population has decreased by -0.68% since the most recent census, which recorded a population of 5,329 in 2020.