| Official Name: | Poplar Plains, Connecticut |
| Settlement Type: | Census-designated place |
| Pushpin Map: | Connecticut#USA |
| Pushpin Label: | Poplar Plains |
| Coordinates: | 41.1686°N -73.3781°W |
| Subdivision Type: | Country |
| Subdivision Type1: | State |
| Subdivision Name1: | Connecticut |
| Subdivision Type2: | County |
| Subdivision Name2: | Fairfield |
| Subdivision Type3: | Town |
| Subdivision Name3: | Westport |
| Area Footnotes: | [1] |
| Area Total Km2: | 2.78 |
| Area Land Km2: | 2.77 |
| Area Water Km2: | 0.01 |
| Population As Of: | 2020 |
| Timezone: | Eastern (EST) |
| Utc Offset: | -5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | -4 |
| Elevation Ft: | 100 |
| Postal Code Type: | ZIP Code |
| Postal Code: | 06880 (Westport) |
| Area Code: | 203/475 |
| Blank Name: | FIPS code |
| Blank Info: | 09-61555 |
| Blank1 Name: | GNIS feature ID |
| Blank1 Info: | 2805091 |
Poplar Plains is a census-designated place (CDP) in the town of Westport, Fairfield County, Connecticut, United States. It occupies the northwest corner of the town and is bordered to the southwest by the city of Norwalk, to the northwest by the town of Wilton, to the northeast by the town of Weston, to the east by the Saugatuck River, and to the south by the Merritt Parkway.
Poplar Plains was first listed as a CDP prior to the 2020 census.