Charles Louis de Secondat, Baron de La Brède et de Montesquieu, generally referred to as simply Montesquieu, was a French judge, man of letters, historian, and political philosopher.

Separation of powers is the division of a state's government into branches, each with separate, independent powers and responsibilities, so that the powers of one branch are not in conflict with others. The typical division into three branches of government, sometimes called the trias politica model, includes a legislature, an executive, and a judiciary. It can be contrasted with the fusion of powers in monarchies, but also parliamentary and semi-presidential systems where there can be overlap in membership and functions between different branches, especially the executive and legislative.