Ammonium iodide is the inorganic compound with the formula NH₄I. A white solid. It is an ionic compound, although impure samples appear yellow. This salt consists of ammonium cation and an iodide anion. It can be prepared by the action of hydroiodic acid on ammonia. It is easily soluble in water, from which it crystallizes in cubes. It is also soluble in ethanol. Ammonium iodide in aqueous solutions are observed as acidic and display elevated vapor pressures at high temperatures.

Ammonium iodide can be made in lab by treating ammonia with hydroiodic acid:

Ammonium iodide is used as dietary supplement to treat iodine deficiency.

Vinyl sulfones have been prepared using ammonium iodide.

In green chemistry, ammonium iodide and an oxidant (e.g., H₂O₂) cleanly iodinate ketones and aromatic compounds.