碘化铵（英文：Ammonium iodide），化学式为NH₄I。常温下呈无色结晶或颗粒。可溶于水、醋酸、氨，易溶于乙醇、丙酮；微溶于乙醚。碘化铵加热后升华，其气体遇光及空气会出现游离碘而呈黄色或褐色。

碘化铵受热分解：

2NH₄I → 2NH₃ + I₂ + H₂

Ammonium iodide is the chemical compound NH₄I. It is used in photographic chemicals and some medications. 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. It gradually turns yellow on standing in moist air, owing to decomposition with liberation of iodine.