| Greenwell State Park | |
| Photo Alt: | Barns |
| Photo Width: | 280 |
| Map: | USA Maryland |
| Map Width: | 280 |
| Relief: | 1 |
| Label: | Greenwell State Park |
| Location: | St. Mary's County, Maryland, United States |
| Nearest Town: | California, Maryland |
| Coordinates: | 38.3689°N -76.5292°W |
| Area: | 596acres |
| Elevation: | 30feet |
| Established: | 1971 |
| Free Label: | Named for |
| Free Data: | John and Mary Greenwell |
| Designation: | Maryland state park |
| Administrator: | Maryland Department of Natural Resources |
Greenwell State Park is a public recreation area located on the Patuxent River in St. Mary's County, Maryland. The state park features the historic Rosedale Manor House as well as the Bonds-Simms tobacco barns complex. Park activities include hiking, cycling, horseback riding, fishing, picnicking, hunting, swimming, and canoeing.
The park originated in 1971, when John Phillip Greenwell, Jr. and his sister, Mary Wallace Greenwell, donated their 167acres farm to the state for use as a public park. The state subsequently purchased the adjacent 430acres Bond property and added it to the park.