氨水（NH₃[aq]）常称为阿摩尼亚水，指氨气的水溶液，有强烈刺鼻气味，具弱碱性。

氨水中，氨气分子发生微弱水解生成氢氧根离子及铵根离子。“氢氧化铵”事实上并不存在，只是对氨水溶液中的离子的描述，并无法从溶液中分离出来。

氨的在水中的电离可以表示为：

反应平衡常数K_b = 1.8×10。

1M氨水的pH值为11.63，大约有0.42%的NH₃变为NH₄。

氨水是实验室中氨的常用来源。它可与含铜(II)离子的溶液作用生成深蓝色的配合物，也可用于配置银氨溶液等分析化学试剂。

Ammonia solution, also known as ammonium hydroxide, ammonia water, ammonical liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or simply ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH₃(aq). Although the name ammonium hydroxide suggests an alkali with composition [NH₄][OH], it is actually impossible to isolate samples of NH₄OH, as these ions do not comprise a significant fraction of the total amount of ammonia except in extremely dilute solutions.