In international law, harmonisation refers to the process by which different states adopt the same laws.

Harmonisation often occurs as a result of the operation of international treaties. The regulatory principles of stronger states are often (but not always) transplanted into weaker ones.

Harmonisation can also refer to the act of removing discrepancies between different Gospels. This was done in the past in many ways, although finally Christianity accepted the Gospels with all their discrepancies.

In music, harmonisation refers to composing a chord.