The largest moons in the Solar System
The top 3 according to 1 vote: Callisto · Ganymede · Titan. (Updated Oct 30, 2025.)
The Solar System's moons ranked by mean radius, from Wikipedia's list of Solar System objects by size. The diameter is roughly twice the radius.
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Top 15
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1
Callisto
Moon of Jupiter, mean radius about 2,410 km. Its surface is covered in craters.
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2
Ganymede
Moon of Jupiter, mean radius about 2,632 km. The largest moon in the Solar System, bigger than Mercury.
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3
Titan
Moon of Saturn, mean radius about 2,575 km. The only moon with a thick atmosphere, with lakes of liquid methane.
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4
Io
Moon of Jupiter, mean radius about 1,824 km. The most volcanically active body in the Solar System.
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5
Moon
Earth's natural satellite, mean radius about 1,737 km. The only other world humans have walked on.
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6
Europa
Moon of Jupiter, mean radius about 1,561 km. Probably hides a liquid ocean under its ice.
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7
Triton
Moon of Neptune, mean radius about 1,353 km. A large moon that orbits backwards, probably a captured object.
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8
Titania
Moon of Uranus, mean radius about 788 km. The largest moon of Uranus.
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9
Rhea
Moon of Saturn, mean radius about 764 km.
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10
Oberon
Moon of Uranus, mean radius about 761 km.
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11
Iapetus
Moon of Saturn, mean radius about 734 km. One half is dark and the other bright.
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12
Charon
Moon of Pluto, mean radius about 606 km. About half the size of Pluto.
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13
Ariel
Moon of Uranus, mean radius about 579 km.
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14
Dione
Moon of Saturn, mean radius about 561 km.
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15
Tethys
Moon of Saturn, mean radius about 531 km.
Candidates
They don't make it into the top 15… yet. Vote for them to move them up.
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16
Enceladus
Moon of Saturn, mean radius about 252 km. Shoots plumes of water ice from its south pole.
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17
Miranda
Moon of Uranus, mean radius about 236 km. Has Verona Rupes, a cliff around 20 km high.
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18
Proteus
Moon of Neptune, mean radius about 210 km.
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19
Mimas
Moon of Saturn, mean radius about 198 km. Its huge Herschel crater makes it look like the Death Star.
How is this ranking ordered? By people's votes: each ▲ adds a point and each ▼ takes one away. Anyone can vote and add what is missing.
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Comments (2)
泰坦有濃厚大氣，是很特別的衛星。
木衛三比水星還大，太誇張了。