| Official Name: | Ploskoseminsky |
| Native Name: | Плоскосеминский |
| Settlement Type: | Settlement |
| Pushpin Map: | Russia Altai Krai#Russia |
| Subdivision Type: | Country |
| Subdivision Name: | Russia |
| Subdivision Name1: | Altai Krai |
| Subdivision Name3: | Rebrikhinsky District |
| Subdivision Type4: | Municipality |
| Utc Offset1: | +7:00 |
| Coordinates: | 52.9833°N 111°W[1] |
Ploskoseminsky (Russian: Плоскосеминский) is a rural locality (a settlement) and the administrative center of Ploskoseminsky Selsoviet, Rebrikhinsky District, Altai Krai, Russia. The population was 359 as of 2013.[2] There are 4 streets.
Ploskoseminsky is located 18 km southeast of Rebrikha (the district's administrative centre) by road. Dalny is the nearest rural locality.[3]