The Chandler wobble is an excited resonance of the Earth's rotation having a period of about 14 months. Although it has been under investigation for more than a century, its excitation mechanism has remained elusive. Here, the angular momentum of the atmosphere computed from the products of a numerical weather prediction analysis system and the angular momentum of the oceans computed from a global oceanic general circulation model driven by observed surface winds and fluxes are used to show that during 1985.0–1996.0 the Chandler wobble was excited by a combination of atmospheric and oceanic processes, with the dominant excitation mechanism being ocean-bottom pressure fluctuations.