| Official Name: | Adair, Illinois |
| Other Name: | Reedyville |
| Settlement Type: | Census-designated place |
| Pushpin Map: | Illinois#USA |
| Pushpin Label: | Adair |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Illinois |
| Subdivision Type2: | County |
| Subdivision Name2: | McDonough |
| Subdivision Type3: | Township |
| Subdivision Name3: | New Salem |
| Unit Pref: | Imperial |
| Area Footnotes: | [1] |
| Area Total Km2: | 1.11 |
| Area Land Km2: | 1.11 |
| Area Water Km2: | 0.00 |
| Area Total Sq Mi: | 0.43 |
| Area Land Sq Mi: | 0.43 |
| Area Water Sq Mi: | 0.00 |
| Population As Of: | 2020 |
| Population Footnotes: | [2] |
| Population Total: | 212 |
| Population Density Km2: | 190.51 |
| Population Density Sq Mi: | 493.02 |
| Timezone: | Central (CST) |
| Utc Offset: | -6 |
| Timezone Dst: | CDT |
| Utc Offset Dst: | -5 |
| Elevation Ft: | 646 |
| Coordinates: | 40.4189°N -90.4967°W |
| Postal Code Type: | ZIP code |
| Postal Code: | 61411 |
| Area Code: | 309 |
| Blank Name: | GNIS feature ID |
| Blank Info: | 403339 |
Adair is an unincorporated community and census-designated place (CDP) in McDonough County, Illinois, United States. It is part of New Salem Township. As of the 2020 census, Adair had a population of 212.[2]
Adair was laid out in August 1870 under the name of "Reedyville"; though the name has never been officially changed, the location is known as Adair because that name was given to the post office.[3]
Adair is in eastern McDonough County, along U.S. Route 136 (Main Street). US 136 leads northwest to Macomb, the county seat, and southeast to Havana. The Burlington Northern Santa Fe Railway runs through the east side of Adair.