Libellus de imperatoria potestate in urbe Roma is an anonymous Latin treatise on "imperial power in the city of Rome". It has been dated as early as the late 9th century and as late as c. 950, and was probably written at Spoleto. It survives in one mansucript, appended to the contemporary Chronicon by Benedict of Sant'Andrea.
The Libellus argues for the authority of the Holy Roman Emperor in the so-called "patrimony of Saint Peter". Ferdinand Gregorovius calls its author an "Imperialist" and a "partisan", and doubts the accuracy of his claim that "[the emperor's] legate resides in Rome at all times". According to Eleanor Duckett, the author of the Libellus "poured out his feelings into that interesting document". The author clearly sides with the Emperor Louis II against Pope Nicholas I.