The Mill River is a river in the Town of Hempstead in Nassau County, on the South Shore of Long Island, in New York, United States.

[1][2] The waters flow towards the south and ultimately into Hewlett Bay.

[3] Communities which the Mill River passes through include East Rockaway, Lynbrook, Rockville Centre, and West Hempstead.

[1][3][4][5] Another Mill River exists on Long Island, located in the Town of Oyster Bay on the North Shore.

[5] Notable communities either partially or wholly within the Mill River Watershed include East Hills, East Rockaway, Garden City, Hempstead, Lakeview, Malverne, Mineola, Oceanside, Old Westbury, Rockville Centre, Roslyn Estates, Roslyn Heights, and West Hempstead.