Io is the innermost Galilean moon of Jupiter and, as such, its distance from the Sun is determined by Jupiter's orbit. Jupiter orbits the Sun at distances that range from 741 million kilometers to 817 million kilometers.
Io maintains a mean orbital distance of 422,000 kilometers from Jupiter. This means that when Jupiter is at its perihelion, with Io between itself and the Sun, Io's distance from the Sun is 740.6 million kilometers. Conversely, when the Jovian system has reached its aphelion and Io swings around to Jupiter's far side, the moon is 817 million kilometers away from the Sun.