A kinase is a type of enzyme that transfers phosphate groups from ATP to a specified substrate or target. Typically, the target is "activated" or "energized" by being phosphorylated. All kinases require a divalent metal ion such as Mg²⁺ or Mn²⁺ to transfer the phosphoryl group. Kinases are studied in biochemistry.

There are many different types of kinases; each named for the target substrate. Some notable kinases are: protein kinase, Janus kinase, tyrosine kinase, focal adhesion kinase, creatine kinase, pyruvate kinase, hexokinase.