In enzymology, an ammonia kinase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are ATP and NH<sub>3</sub>, whereas its two products are ADP and phosphoramide.
This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with a nitrogenous group as acceptor. The systematic name of this enzyme class is ATP:ammonia phosphotransferase. Other names in common use include phosphoramidate-adenosine diphosphate phosphotransferase, and phosphoramidate-ADP-phosphotransferase.