Snapping shrimp produce a loud crackling noise that is intense enough to disturb underwater communication. This sound originates from the violent collapse of a large cavitation bubble generated under the tensile forces of a high-velocity water jet formed when the shrimp's snapper-claw snaps shut (<figr rid="f1">Fig. 1</figr>). Here we show that a short, intense flash of light is emitted as the bubble collapses, indicating that extreme pressures and temperatures of at least 5,000 K (ref. 4) must exist inside the bubble at the point of collapse. We have dubbed this phenomenon 'shrimpoluminescence' - the first observation, to our knowledge, of this mode of light production in any animal - because of its apparent similarity to sonoluminescence, the light emission from a bubble periodically driven by ultrasound.