Ammonia is a compound of nitrogen and hydrogen with the formula NH₃. It is a colourless gas with a pungent smell. Ammonia is the simplest pnictogen hydride and the lightest stable binary hydride.

Ammonia is a common nitrogen fertilizer, and it is also used in the production of nitric acid, explosives, and other chemicals. Ammonia is also used in the refrigeration industry and as a cleaning agent.

The term "ammonia" can also refer to a solution of ammonia in water, which is also called ammonium hydroxide. Ammonium hydroxide is a weak base, and it is used in the manufacture of soaps, detergents, and other cleaning products.