| Posey Island State Park | |
| Map: | USA Washington#USA |
| Relief: | 1 |
| Location: | San Juan County, Washington, United States |
| Coordinates: | 48.6183°N -123.1678°W |
| Area Acre: | 1 |
| Elevation: | 13feet |
| Designation: | Washington marine state park |
| Established: | 1960 |
| Website: | Posey Island State Park |
Posey Island State Park is a popular recreation area consisting of 1acres Posey Island in San Juan County, Washington. The island is located north of Pearl Island, near Roche Harbor, San Juan Island. It has about 1000feet of saltwater shoreline and is part of the Cascadia Marine Trail, with campsites restricted to visitors arriving in non-motorized watercraft. The island-park is managed by the Washington State Parks and Recreation Commission. It became a state park in 1960 under lease from the U.S. Bureau of Land Management.