巯基乙酸，结构式HSCH₂COOH。

纯品为无色有令人不愉快气味的透明液体，工业品常为无色至微黄色。与水、乙醇、乙醚混溶。露置于空气中时，迅速发生氧化，少量金属离子可以加速氧化过程。浓度小于70％（重量）的巯基乙酸水溶液，在室温下一般是稳定的。

Thioglycolic acid (TGA) is the organic compound HSCH₂CO₂H. TGA is often called mercaptoacetic acid (MAA). It contains both a thiol (mercaptan) and carboxylic acid functional groups. It is a colorless liquid with a strongly unpleasant odor. TGA is miscible with polar organic solvents.