Taurine (), or 2-aminoethanesulfonic acid, is a non-proteinogenic amino sulfonic acid that is widely-distributed in animal tissues. It is a major constituent of bile and can be found in the large intestine, and accounts for up to 0.1% of total human body weight. It is named after Latin taurus (cognate to Ancient Greek ταῦρος, taûros) meaning bull or ox, as it was first isolated from ox bile in 1827 by German scientists Friedrich Tiedemann and Leopold Gmelin. It was discovered in human bile in 1846 by Edmund Ronalds.

It has many biological roles, such as conjugation of bile acids, antioxidation, osmoregulation, membrane stabilization, and modulation of calcium signaling. It is essential for cardiovascular function, and development and function of skeletal muscle, the retina, and the central nervous system.

Taurine concentrations in land plants are very low or undetectable, but up to 1000 nmol/g wet weight have been found in algae.

It is an unusual example of a naturally occurring sulfonic acid.