Rex River
General data
- Name: Rex River
- Water system: Lake Washington
- Water type: River
- Progression: Chester Morse Lake -> Cedar River (Washington) -> Lake Washington -> Lake Washington Ship Canal -> Puget Sound -> Salish Sea -> Pacific Ocean -> Planet Earth
- Climates: Temperate
- Continents: North America
- Countries: United States of America
The Rex River is a river in the U.S. state of Washington. It originates near the crest of the Cascade Mountains and flows northwest to join the Cedar River in the Chester Morse Lake reservoir. The Cedar River flows to Lake Washington and, ultimately, Puget Sound. Tributaries of the Rex River include Pine Creek, Lindsay Creek, and Boulder Creek.