4‑Hydroxy­benzaldehyde (para‑hydroxy­benzaldehyde) is an organic compound with the formula C6H4OH(CHO).

4-Hydroxybenzaldehyde is prepared by reaction of phenol with chloroform, which gives isomeric hydroxybenzal chlorides.

Hydrolysis of the C-Cl bonds gives the aldehyde.

In the Dakin oxidation, 4-hydroxybenzaldehyde reacts with hydrogen peroxide in base to form hydroquinone.

p-Hydroxybenzaldehyde dehydrogenase is an enzyme found in carrots (Daucus carota).