m-Phenylenediamine, also called 1,3-diaminobenzene, is an organic compound with the formula C6H4(NH2)2. It is an isomer of o-phenylenediamine and p-phenylenediamine. This aromatic diamine is a colourless solid that appears as needles, but turns red or purple on exposure to air due to formation of oxidation products. Samples often come as colourless flakes and may darken in storage.