Stillwater River may refer to:
New Zealand
- Stillwater River (New Zealand), on the South Island
United States
- Stillwater River (Maine)
- Stillwater River (Nashua River tributary), Massachusetts
- Stillwater River (Stillwater County, Montana), a tributary of the Yellowstone River
- Stillwater River (Flathead County, Montana), a tributary of the Whitefish River
- Stillwater River (Ohio)
- Stillwater River (Rhode Island)
See also
- Stillwater (disambiguation)