Cyameluric acid or 2,5,8-trihydroxy-s-heptazine is a chemical compound with formula C6N7O3H3, usually described as a heptazine molecule with the hydrogen atoms replaced by hydroxyl groups –OH; or any of its tautomers.

In 1834 Justus von Liebig described the compounds that he named melamine, melam, and melon.

[3] In the following years Liebig prepared the same salts by other methods, such as by fusing potassium thiocyanate with antimony trichloride,[4] and eventually determined the formula C9N13H3 for the acid.

[5][6] Cyameluric acid, H3O3C6N7 and salts were prepared in 1850 by W. Henneberg, by treating Gmelin's "hydromelonate" with alkali.

His structure was in fact a meta-cyclophane, but it is remarkable since at that time cyclic compounds of any type were not widely recognised.