A triazole is a heterocyclic compound featuring a five-membered ring of two carbon atoms and three nitrogen atoms with molecular formula C₂H₃N₃. Triazoles exhibit substantial isomerism, depending on the positioning of the nitrogen atoms within the ring.

Many triazoles are versatile, biologically active compounds commonly used as fungicides and plant retardants. However, triazoles are also useful in bioorthogonal chemistry, because the large number of nitrogen atoms causes triazoles to react similar to azides. Lastly, the many free lone pairs in triazoles make them useful as coordination compounds, although not typically as haptic ligands.