| Castle Creek | |
| Pushpin Map: | Washington |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | U.S. State |
| Subdivision Name2: | Washington |
| Subdivision Type3: | County |
| Subdivision Name3: | Cowlitz |
| Subdivision Type4: | County |
| Subdivision Name4: | Skamania |
| Source1 Location: | West flank of Mount St. Helens |
| Source1 Coordinates: | 46.2169°N -122.2393°W |
| Source1 Elevation: | 4,275 feet |
| Mouth: | North Fork Toutle River |
| Mouth Coordinates: | 46.283°N -122.2936°W |
| Mouth Elevation: | 2,200 feet |
| Tributaries Left: | South Fork Castle Creek |
| Waterbodies: | Castle Lake (South Fork) |
Castle Creek is a tributary of the North Fork Toutle River on the flank of Mount St. Helens in Washington state. It rises about two miles (three kilometers) northwest of the crater rim (46.2169°N -122.2393°W) and flows generally to the northwest. The outflow of Castle Lake joins the creek at the lake's north end (46.258°N -122.272°W) after traveling a few hundred meters on the South Fork Castle Creek.[1] It joins the North Fork Toutle River at 46.283°N -122.2936°W, elevation 2,200 feet.[1]
Castle Lake was created by an avalanche subsequent to the May 18, 1980 eruption of Mount St. Helens which blocked South Fork Castle Creek.[2] Pre-1980 maps show this area as "Castle Creek Marsh".[3] [4]