Three recent close flybys of Io by the Galileo spacecraft, and new observations from the Hubble Space Telescope and ground-based telescopes, have greatly advanced our understanding of Jupiter’s volcanic moon Io. Io’s volcanos are much hotter than previously suspected, perhaps requiring exotic silicate magma compositions. Despite much new data, Io’s largest volcano, Loki, is still poorly understood. New data on Io’s plumes suggest the existence of two types of plumes: primary plumes, relatively rich in S2 gas, which are emitted where magma first reaches the surface, and secondary plumes, more SO2 rich, which result from interaction of lava flows with a volatile-rich substrate.