Christiaan Huygens, FRS (English pronunciation: /ˈhaɪɡənz/, [ˈɦœyɣə(n)s] ( listen); (14 April 1629 – 8 July 1695) was a prominent Dutch mathematician, astronomer, physicist and horologist. His work included early telescopic studies elucidating the nature of the rings of Saturn and the discovery of its moon Titan, the invention of the pendulum clock and other investigations in timekeeping, and studies of both optics and the centrifugal force.

Huygens achieved note for his argument that light consists of waves, now known as the Huygens–Fresnel principle, which two centuries later became instrumental in the understanding of wave-particle duality. He generally receives credit for his discovery of the centrifugal force, the laws for collision of bodies, for his role in the development of modern calculus and his original observations on sound perception (see repetition pitch).