A tank car is a type of railroad car, consisting of a large tank with one or more compartments, and usually used for transportation of liquids, but occasionally substances in powder form. Chemicals such as chlorine and hydrochloric acid, and foods such as corn syrup are carried in tank cars.

The capacity of a tank car typically ranges from around 10,000 gallons to 30,000 gallons. A major manufacturer of tank cars is the Union Tank Car Company, whose identifying letters are UTLX.