Sour Lake is a city in Hardin County, Texas, United States. The population was 1,813 at the 2010 census. It was originally named "Sour Lake Springs", after the sulphurous spring water that flowed into the nearby lake. The city is part of the Beaumont–Port Arthur Metropolitan Statistical Area. Sour Lake is the oldest surviving town in Hardin County. It is called by some the "Gateway to the Big Thicket".
Sour Lake was first settled around 1835 when the Mexican state of Coahuila y Tejas granted Stephen Jackson one league of land covering 4,428 acres (17.92 km2) by land grant. Sam Houston visited Sour Lake in his later years. The town is home to one of the biggest sinkholes in Texas.
Sour Lake became a short-lived boomtown with the discovery of oil in 1901, shortly after oil was found at the nearby Spindletop salt dome. It is known as the birthplace of Texaco. Formed in 1903, the Texas Company (Texaco's former corporate name) is one of the three major oil companies that can trace its origins to the oil fields around Southeast Texas.