| Jonathan Alder High School | |
| Streetaddress: | 9200 U.S. Route 42 S |
| City: | Plain City |
| State: | Ohio |
| County: | (Madison County) |
| Zipcode: | 43064 |
| Coordinates: | 40.0781°N -83.2878°W |
| District: | Jonathan Alder Local Schools |
| Superintendent: | Gary Chapman |
| Principal: | Clint Hayes[1] |
| Teaching Staff: | 28.37 (FTE) |
| Ratio: | 24.22 |
| Type: | Public, Coeducational high school |
| Grades: | 9-12 |
| Campus: | Rural |
| Conference: | Central Buckeye Conference |
| Accreditation: | North Central Association of Colleges and Schools[2] |
| Team Name: | Pioneers[3] |
| Newspaper: | Pioneer Press |
| Opened: | 1957 |
| Enrollment: | 687 (2022-23)[4] |
| Homepage: | http://www.alder.k12.oh.us |
Jonathan Alder High School is an NCA accredited public high school located in Plain City, Ohio. It is the only high school in the Jonathan Alder Local School District. The school, as well as the district, are named after Jonathan Alder, the first white settler in Madison County.
The current building was first occupied in the 2005–2006 school year. The original Jonathan Alder High School was built at 6440 Kilbury-Huber Rd., and was turned into a Junior High School when the new building was built.