Charles Louis de Secondat, Baron de La Brède et de Montesquieu (French pronunciation: ​[ʃaʁl lwi də səɡɔ̃da baʁɔ̃ də la bʁɛd e də mɔ̃tɛskjø]; 18 January 1689 – 10 February 1755), generally referred to as simply Montesquieu (US: , UK also , French: [mɔ̃tɛskjø]), was a French judge, man of letters, historian, and political philosopher.

He is the principal source of the theory of separation of powers, which is implemented in many constitutions throughout the world. He is also known for doing more than any other author to secure the place of the word despotism in the political lexicon. His anonymously published The Spirit of Law (1748), which was received well in both Great Britain and the American colonies, influenced the Founding Fathers of the United States in drafting the U.S. Constitution.