| Smallwood State Park | |
| Photo Alt: | House |
| Photo Width: | 280 |
| Map: | USA Maryland |
| Map Width: | 280 |
| Relief: | 1 |
| Label: | Smallwood State Park |
| Location: | Charles County, Maryland, United States |
| Nearest Town: | Marbury, Maryland |
| Coordinates: | 38.5564°N -77.1853°W |
| Area: | 984acres |
| Elevation: | 3feet |
| Established: | 1957 |
| Designation: | Maryland state park |
| Administrator: | Maryland Department of Natural Resources |
Smallwood State Park is a public recreation and historic preservation area located on Mattawoman Creek near Marbury, Charles County, Maryland. The state park preserves Smallwood's Retreat, the plantation home of former Continental Army officer and Governor of Maryland, Major General William Smallwood. The park's include a marina, boat ramps, picnicking facilities, campsites, cabins, trails, and nature center.
After a succession of occupants left Smallwood's Retreat a "standing ruin", a group of local citizens organized the Smallwood Foundation to restore the historic house. The house and ten surrounding acres were acquired in 1938. In 1957, the state began property acquisition for Smallwood State Park, purchasing 323 farmland acres from three owners. The park saw its formal dedication in 1958, when the Smallwood Foundation transferred the ten acres containing the restored Smallwood's Retreat to the state.