Minimum harmonisation is a term used in European Union law.
If a piece of law (usually a directive, but also a regulation on occasion), is described as minimum harmonisation, that means that it sets a threshold which national legislation must meet. However, national law may exceed the terms of the legislation if desired.
It is usually easier to reach agreement on legislation drafted on this basis, as it allows existing national legislation on issues such as consumer protection or the environment to remain in place. Therefore, most European legislation has been implemented on this basis. In more recent years, however, the burden of EC law has led to calls for deregulation, and accusations that some member states still indulge in protectionism when implementing directives into national law through gold-plating. Therefore, a growing minority of EU law contains maximum harmonisation provisions.
It is quite common for a directive or recommendation to consist of a mixture of maximum harmonisation and minimum harmonisation clauses.