In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specified substrates or target molecules; the process is termed "phosphorylation". Generally, the purpose of phosphorylation is to "activate" or "energize" a molecule, increasing its energy so it is able to participate in a subsequent reaction with a negative free energy change. All kinases require a divalent metal ion such as Mg²⁺ or Mn²⁺ to be present, which stabilizes the high-energy bonds of the donor molecule and allows phosphorylation to occur.

There are many different types of kinases; each named for the target substrate. Some notable kinases are:

• Protein kinase (see there for more details);
• Janus kinase;
• Tyrosine kinase;
• Focal adhesion kinase ;
• Creatine kinase;
• Pyruvate kinase;
• Hexokinase.