2-Tolidine (orthotolidine, o-tolidine; not to be confused with o-toluidine) is an organic compound with the chemical formula (C6H4(CH3)NH2)2.

It is a colorless compound although commercial samples are often colored.

It forms salts with acids, such as the hydrochloride, which is commercially available.

[3] 2-Tolidine is an intermediate for the production of soluble azo dyes and insoluble pigments used particularly in the textile, leather and paper industries.

2-Tolidine was widely used as a reagent or indicator in analytical, clinical and forensic chemistry, such as in the analytical determination of gold, or determination of the chlorine level in swimming pool water.