Imidazole (ImH) is an organic compound with the formula C₃N₂H₄. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole, and has non-adjacent nitrogen atoms in meta-substitution.

Many natural products, especially alkaloids, contain the imidazole ring. These imidazoles share the 1,3-C₃N₂ ring but feature varied substituents. This ring system is present in important biological building blocks, such as histidine and the related hormone histamine. Many drugs contain an imidazole ring, such as certain antifungal drugs, the nitroimidazole series of antibiotics, and the sedative midazolam.

When fused to a pyrimidine ring, it forms a purine, which is the most widely occurring nitrogen-containing heterocycle in nature.

The name "imidazole" was coined in 1887 by the German chemist Arthur Rudolf Hantzsch (1857–1935).