Mamaroneck River
General data
- Name: Mamaroneck River
- Water system: Atlantic Ocean
- Water type: River
- Progression: Mamaroneck Harbor (Long Island Sound) -> Long Island Sound -> Atlantic Ocean -> Planet Earth
- Climates: Temperate
- Continents: North America
- Countries: United States of America
The Mamaroneck River is a freshwater stream located in Southern Westchester County, New York.
The river forms in White Plains and Harrison and flows 7.3 miles (11.7 km) south through Mamaroneck Town and Village, where it empties into Mamaroneck Harbor and Long Island Sound. The name of the river comes from a local native American word meaning, "where the fresh water meets the salt water." The river flows into Long Island Sound.