4-Iodobenzoic acid, or p-iodobenzoic acid, is an isomer of iodobenzoic acid.

[3] X-ray crystallography of 4-iodobenzoic acid has shown that it crystallizes in the solid state as hydrogen-bonded dimers which stack perpendicular to their aromatic rings.

The iodine atoms of adjacent dimers are also oriented towards each other due to van der Waals forces.

[4] 4-Iodobenzoic acid may be prepared in the laboratory by the oxidation of p-iodotoluene with potassium permanganate.

[5] The carboxylic acid functionality of 4-iodobenzoic acid undergoes Fischer–Speier esterification with methanol to form the ester methyl 4-iodobenzoate.