Ranked · Updated May 2026

Largest Moons in the Solar System.

The solar system has over 290 confirmed moons. These are the largest, ranked by diameter, with their parent body and the one fact that makes each notable.

1. 5,268 km Ganymede Larger than Mercury. Has its own magnetic field.
2. 5,150 km Titan Only moon with a substantial atmosphere; methane lakes on the surface.
3. 4,821 km Callisto Most heavily cratered object in the solar system.
4. 3,643 km Io Most volcanically active body known.
5. 3,474 km Moon Largest moon relative to its planet (Pluto-Charon excepted).
6. 3,122 km Europa Subsurface ocean. Prime astrobiology target.
7. 2,707 km Triton Only large moon with a retrograde orbit.
8. 1,578 km Titania Largest moon of Uranus; has a thin CO₂ atmosphere.
9. 1,527 km Rhea Saturn's second-largest moon.
10. 1,523 km Oberon Outermost major moon of Uranus.

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