Ammonium chloride is an inorganic chemical compound with the chemical formula NH₄Cl, also written as [NH₄]Cl. It is an ammonium salt of hydrogen chloride. It consists of ammonium cations [NH₄]⁺ and chloride anions Cl⁻. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. In its naturally occurring mineralogic form, it is known as salammoniac. The mineral is commonly formed on burning coal dumps from condensation of coal-derived gases. It is also found around some types of volcanic vents. It is mainly used as fertilizer and a flavouring agent in some types of liquorice. It is a product of the reaction of hydrochloric acid and ammonia.

It is a product of the Solvay process used to produce sodium carbonate:

Not only is that method the principal one for the manufacture of ammonium chloride, but also it is used to minimize ammonia release in some industrial operations.

Ammonium chloride is prepared commercially by combining ammonia (NH₃) with either hydrogen chloride (gas) or hydrochloric acid (water solution):

Ammonium chloride occurs naturally in volcanic regions, forming on volcanic rocks near fume-releasing vents (fumaroles). The crystals deposit directly from the gaseous state and tend to be short-lived, as they dissolve easily in water.

Ammonium chloride appears to sublime upon heating but actually reversibly decomposes into ammonia and hydrogen chloride gas:

Ammonium chloride reacts with a strong base, like sodium hydroxide, to release ammonia gas:

Similarly, ammonium chloride also reacts with alkali-metal carbonates at elevated temperatures, giving ammonia and alkali-metal chloride: