Ganymede

5,268 km

Largest moon in the solar system

Confirmed Planets and moons · Verified 2026-10-29 · WWV-SP-002

Jupiter's moon Ganymede measures 5,268 km across, which makes it wider than the planet Mercury. It is the only moon known to have its own magnetic field.

Mercury is wider but Ganymede is less massive, because Mercury is far denser.

Sources

Caltech IPAC Cool Cosmos
Universe Today