Catechol (/ˈkætɪtʃɒl/), also known as pyrocatechol or 1,2-dihydroxybenzene, is an organic compound with the molecular formula C₆H₄(OH)₂. It is the ortho isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amounts. It was first discovered by destructive distillation of the plant extract catechin. About 20 million kg are now synthetically produced annually as a commodity organic chemical, mainly as a precursor to pesticides, flavors, and fragrances.

Catechol occurs as feathery white crystals that are very rapidly soluble in water.

(The name "catechol" has also been used as a chemical class name, where it refers generally to the catechins.)

Catechol was first isolated in 1839 by Edgar Hugo Emil Reinsch (1809 - 1884) by distilling it from the solid tannic preparation catechin, which is the residuum of catechu, the boiled or concentrated juice of Mimosa catechu (Acacia catechu L.f). Upon heating catechin above its decomposition point, a substance that Reinsch first named Brenz-Katechusäure (burned catechu acid) sublimated as a white efflorescence. This was a thermal decomposition product of the flavanols in catechin. In 1841, both Wackenroder and Zwenger independently rediscovered catechol; in reporting on their findings, Philosophical Magazine coined the name pyrocatechin. By 1852, Erdmann realized that catechol was benzene with two oxygen atoms added to it; in 1867, August Kekulé realized that catechol was a diol of benzene, so by 1868, catechol was listed as pyrocatechol. In 1879, the Journal of the Chemical Society recommended that catechol be called "catechol", and in the following year, it was listed as such.

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