Leopold III of Lippe was the sovereign of the Principality of Lippe reigning from 1851 until his death.

Lippe was a state in Germany, ruled by the House of Lippe. It was located between the Weser river and the southeast part of the Teutoburg Forest. It originated as a state during the Holy Roman Empire, and was promoted to the status of principality in 1789. During this period the ruling house split into a number of branches, with the main line residing at Detmold. During the Reformation, Lippe had converted to Lutheranism in 1538 and then to Calvinism in 1604.