Sabine Lake in the context of Gulf Intracoastal Waterway

The Sabine River (/səˈbiːn/) is a 360-mile (580 km) long river in the Southern U.S. states of Texas and Louisiana, From the 32nd parallel north and downstream, it serves as part of the boundary between the two states and empties into Sabine Lake, an estuary of the Gulf of Mexico.

Over the first half of the 19th century, the river formed part of the Spanish–American, Mexican–American, and Texan–American international boundaries. The upper reaches of the river flow through the prairie country of northeast Texas. Along much of its lower reaches, it flows through pine forests along the Texas–Louisiana border, and eventually the bayou country near the Gulf Coast.

The U.S. state of Texas has a series of estuaries along its coast on the Gulf of Mexico, most of them bounded by the Texas barrier islands. Estuaries are coastal bodies of water in which freshwater from rivers mixes with saltwater from the sea. Twenty-one drainage basins terminate along the Texas coastline, forming a chain of seven major and five minor estuaries: listed from southwest to northeast, these are the Rio Grande Estuary, Laguna Madre, the Nueces Estuary (Corpus Christi Bay), the Mission–Aransas Estuary (Aransas Bay), the Guadalupe Estuary (San Antonio Bay), the Colorado–Lavaca Estuary (Matagorda Bay), East Matagorda Bay, the San Bernard River and Cedar Lakes Estuary, the Brazos River Estuary, Christmas Bay, the Trinity–San Jacinto Estuary (Galveston Bay), and the Sabine–Neches Estuary (Sabine Lake). Each estuary is named for its one or two chief contributing rivers, excepting Laguna Madre, East Matagorda Bay, and Christmas Bay, which have no major river sources. The estuaries are also sometimes referred to by the names of their respective primary or central water bodies, though each also includes smaller secondary bays, inlets, or other marginal water bodies.

These water bodies include some of the largest and most ecologically productive coastal estuaries in the United States and contribute significantly to the ecological and economic resources of Texas. They are included in a number of national protected areas such as National Wildlife Refuges, a National Seashore, and a National Estuarine Research Reserve, as well as various state parks and other regional protected areas. The two most economically important (the Nueces and Trinity–San Jacinto Estuaries) have been designated by the United States Environmental Protection Agency as estuaries of national significance under the National Estuary Program. The Gulf Intracoastal Waterway runs through each of the major estuaries, linking Texas ports with others along the Gulf Coast of the United States.

The Neches River (/ˈneɪtʃɪz/) begins in Van Zandt County west of Rhine Lake and flows for 416 miles (669 km) through the piney woods of east Texas, defining the boundaries of 14 counties on its way to its mouth on Sabine Lake near the Rainbow Bridge. Two major reservoirs, Lake Palestine and B. A. Steinhagen Reservoir are located on the Neches. The Angelina River (containing Sam Rayburn Reservoir) is a major tributary with its confluence at the north of Lake B. A. Steinhagen. Tributaries to the south include Village Creek and Pine Island Bayou, draining much of the Big Thicket region, both joining the Neches a few miles north of Beaumont. Towns and cities located along the river including Tyler, Lufkin, and Silsbee, although significant portions of the Neches River are undeveloped and flow through protected natural lands. In contrast, the lower 40 miles of the river are a major shipping channel, highly industrialized, with a number of cities and towns concentrated in the area including Beaumont, Vidor, Port Neches, Nederland, Groves, and Port Arthur.