Green Lake is a natural tidal lake in Calhoun County, Texas, on the Guadalupe River flood basin. Known for its greenish waters, from which its name derives, the lake is located 12 miles (19 km) west of Port Lavaca and 22 miles (35 km) south of Victoria on the Gulf Coastal Plain. Despite being less than 3 miles (4.8 km) from the coast of San Antonio Bay, its waters are fresh. It is the largest natural freshwater lake entirely in Texas, covering an area of approximately 10,000 acres (40 km²).