| Douglas State Forest | |
| Map: | USA Massachusetts#USA |
| Map Size: | 280 |
| Relief: | 1 |
| Location: | Douglas, Worcester, Massachusetts, United States |
| Coordinates: | 42.0583°N -71.7869°W |
| Area Acre: | 5525 |
| Elevation: | 702feet |
| Established: | 1934 |
| Governing Body: | Massachusetts Department of Conservation and Recreation |
| Website: | Douglas State Forest |
Douglas State Forest is a publicly owned forest with recreational features located in the town of Douglas, Massachusetts, bordering both Connecticut and Rhode Island. The state forest's include Wallum Lake and a rare Atlantic white cedar swamp, of which are designated as a Massachusetts Wildland. The forest is managed by the Massachusetts Department of Conservation and Recreation.
The state forest was created through the state's purchase of in 1934. In the 1930s, the Civilian Conservation Corps installed major improvements including a picnic pavilion, an administrative building, and water management infrastructure.
Forest trails are used for hiking, biking, horseback riding, and cross-country skiing. A 7.8miles section of the 92adj=midNaNadj=mid Midstate Trail runs through the forest as does a portion of the 22adj=midNaNadj=mid Southern New England Trunkline Trail. At the southwest extreme of the park, the tri-state marker, where Connecticut, Massachusetts and Rhode Island are conjoined, may be reached by a short offshoot of the Mid-State Trail.
Wallum Lake offers fishing, swimming, and boating. The forest also offers picnicking, restricted hunting, and a group day-use area.