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 sulphur was a sign of the crude oil that lay in proximity to local groundwater. The city is part of the Beaumont–Port Arthur Metropolitan Statistical Area. Sam Houston visited Sour Lake in his later years. The town is also home to one of the biggest sinkholes in Texas.

Sour Lake is the oldest surviving town in Hardin County. Sour Lake was first settled around 1835 when the Mexican State of Coahuilla y Tejas granted Stephen Jackson one league of land covering 4,428 acres (17.92 km²) by land grant. It is called by some the "Gateway to the Big Thicket".

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 corporate name) is one of the three major oil companies that can trace its origins to the oil fields around Southeast Texas. The Sour Lake oilfield produced about 90,000,000 barrels (14,000,000 m³) of oil up to 1948, when it was producing about 3,500 barrels (560 m³) daily and new drilling was still underway. Today the Sour Lake oilfield is the oldest continuously-producing oil field in the world.

The town of Atcheson in Bruce McCandless's 2012 novel Sour Lake appears to be based at least loosely on the real Sour Lake. Atcheson, like the real-life Sour Lake, is situated in the Big Thicket and experienced a short-lived oil boom in early years of the 20th Century. Yvette Benavides, in a San Antonio Express-News review of the book, noted, "There is a lot that is historically factual in this novel. That's part of the fun of reading Sour Lake.”