The Foucault pendulum ( ; ), or Foucault's pendulum, named after the French physicist Léon Foucault, is a simple device conceived as an experiment to demonstrate the rotation of the Earth. While it had long been known that the Earth rotates, the introduction of the Foucault pendulum in 1851 was the first simple proof of the rotation in an easy-to-see experiment. Today, Foucault pendulums are popular displays in science museums and universities.

Foucault's Pendulum (original title: Il pendolo di Foucault ) is a novel by Italian writer and philosopher Umberto Eco. It was first published in 1988, and an English translation by William Weaver appeared a year later.