The Laguna Madre is a long, shallow, hypersaline lagoon along the western coast of the Gulf of Mexico in Nueces, Kenedy, Kleberg, Willacy and Cameron Counties in Texas, United States. It is one of seven major estuaries along the Gulf Coast of Texas. The roughly 20-mile (32 km) long Saltillo Flats land bridge divides it into Upper and Lower lagoons joined by the Intracoastal Waterway, which has been dredged through the lagoon. Cumulatively, Laguna Madre is approximately 130 miles (210 km) long, the length of Padre Island in the US. The main extensions include Baffin Bay in Upper Laguna Madre, Red Fish Bay just below the Saltillo Flats, and South Bay near the Mexican border. As a natural ecological unit, the Laguna Madre of the United States is the northern half of the ecosystem as a whole, which extends into Tamaulipas, Mexico approximately 144 miles (232 km) south of the US border, to the vicinity of the Rio Soto La Marina and the town of La Pesca, extending approximately 275 miles (443 km) through USA and Mexico in total.

The Intracoastal Waterway (ICW) is a 3,000-mile (4,800 km) inland waterway along the Atlantic and Gulf of Mexico coasts of the United States, running from Massachusetts southward along the Atlantic Seaboard and around the southern tip of Florida, then following the Gulf Coast to Brownsville, Texas. Some sections of the waterway consist of natural inlets, saltwater rivers, bays, and sounds, while others are artificial canals. It provides a navigable route along its length without many of the hazards of travel on the open sea.