Which moon in the solar system has active volcanoes?

Io: Jupiter's innermost moon, Io, is the most volcanically active body in our entire solar system! This surprises most people because Io's great distance from the sun and its icy surface make it seem like a very cold place.

NASA missions imaged massive plumes shooting hundreds of kilometers above the surface, active lava flows and walls of fire associated with magma flowing from fissures.