The Hudson-Raritan Estuary is a system of bays and tidal rivers where the Hudson, Hackensack, Passaic, Rahway, and Raritan rivers meet the Atlantic Ocean. It includes New York's pristine Jamaica Bay Wildlife Refuge, as well as the busiest harbor in the entire world, Upper New York Bay.

Development along the shoreline has caused much pollution to build up in the estuary over time, particularly from the large cities around the estuary, including New York City and Newark, New Jersey. Many groups have changed their practices and experimented with new techniques to improve the health of the estuary system, including planting beds of oysters, a shellfish that filters pollutants out of the water.

The Hudson River gets its name from English explorer Henry Hudson who sailed his ship, the Half Moon, up the waterway along with his crew of Dutch and British sailors up towards present-day Albany, New York on September 3, 1609. Hudson and his crew thought it might be a new route to the Far East region of Asia. The Half Moon had been searching for that route, the Northwest Passage, from Scandinavia to present-day Maine and South Carolina.

The Raritan River takes its name from an Algonquin word. Algonquin is a language group shared by many tribes in the eastern United States at the time of Henry Hudson's arrival to the area.