As of 2026-07-08, Triton tops the list with 2,700 km.
- #1 Triton — 2,700 km
largest moon of Neptune
Triton is the largest natural satellite of the planet Neptune. It is the only moon of Neptune massive enough to be rounded under its own gravity and hosts a thin, hazy atmosphere. Triton orbits Neptune in a retrograde orbit—revolving in the opposite direction to the parent planet's rotation—the only large moon in the Solar System to do so. Triton is thought to have once been a dwarf planet from the Kuiper belt, captured into Neptune's orbit by the latter's gravity. Read more on Wikipedia.
Wikidata - #2 Nereid — 360 km
large moon of Neptune
Nereid, or Neptune II, is the third-largest moon of Neptune. It has the second-most eccentric orbit of all known moons in the Solar System, after S/2023 S 38. It was the second moon of Neptune to be discovered, by Gerard Kuiper in 1949. Read more on Wikipedia.
Wikidata - #3 Phoebe — 220 km
moon of Saturn
Phoebe is the most massive irregular satellite of Saturn with a mean diameter of 213 km (132 mi). It was discovered by William Henry Pickering on 18 March 1899 from photographic plates that had been taken by DeLisle Stewart starting on 16 August 1898 at the Boyden Station of the Carmen Alto Observatory near Arequipa, Peru. It was the first natural satellite to be discovered photographically. Read more on Wikipedia.
Wikidata - #4 Sycorax — 165 km
moon of Uranus
Sycorax is the largest irregular moon of Uranus, with a diameter of approximately 157 km. It was discovered on 6 September 1997 on the Hale Telescope in California. Sycorax's orbit is retrograde, irregular, and much more distant than that of Oberon, the furthest of Uranus's regular moons. It has been hypothesized that Sycorax is a captured object, as opposed to one that formed with Uranus. Read more on Wikipedia.
Wikidata - #5 Halimede — 62,000 m
moon of Neptune
Halimede, or Neptune IX, is a retrograde irregular satellite of Neptune. It was discovered by Matthew J. Holman, John J. Kavelaars, Tommy Grav, Wesley C. Fraser and Dan Milisavljevic on August 14, 2002. Read more on Wikipedia.
Wikidata - #6 Neso — 60,000 m
moon of Neptune
Neso, also known as Neptune XIII and previously as S/2002 N 4, is the second-outermost known moon of Neptune, behind S/2021 N 1. It was discovered on 14 August 2002 by Matthew Holman, JJ Kavelaars, Tommy Grav, Wesley Fraser, and Dan Milisavljevic at Cerro Tololo Inter-American Observatory in Chile. Named after one of the Nereids from Greek mythology, Neso orbits Neptune at an average distance of 49.9 million km (31.0 million mi)—almost as far as Mercury's orbital distance from the... Read more on Wikipedia.
Wikidata - #7 Siarnaq — 39,000 m
moon of Saturn
Siarnaq is the second-largest irregular moon of Saturn. It was discovered on 23 September 2000 by a team of astronomers led by Brett J. Gladman. It was named after the Inuit goddess of the sea, Siarnaq, who is more commonly known as Sedna. Siarnaq is the largest member of Saturn's Inuit group of prograde irregular moons, which orbit far from Saturn in the same direction as the planet's rotation. The moons of the Inuit group are believed to have originated as fragments from the collisional... Read more on Wikipedia.
Wikidata - #8 Psamathe — 38,000 m
moon of Neptune
Psamathe, also known as Neptune X, is a retrograde irregular satellite of Neptune. It is named after Psamathe, one of the Nereids. Psamathe was discovered by Scott S. Sheppard and David C. Jewitt in 2003 using the 8.2 meter Subaru Telescope. Before it was officially named on February 3, 2007, it was known by the provisional designation S/2003 N 1. Read more on Wikipedia.
Wikidata - #9 Albiorix — 29,000 m
moon of Saturn
Albiorix, also known as Saturn XXVI, is the largest member of the Gallic group and Saturn's third-largest irregular moon. Read more on Wikipedia.
Wikidata - #10 Paaliaq — 25,000 m
moon of Saturn
Paaliaq is a prograde irregular satellite of Saturn. It was discovered by J. J. Kavelaars, Brett J. Gladman, Jean-Marc Petit, Hans Scholl, Matthew J. Holman, Brian G. Marsden, Philip D. Nicholson and Joseph A. Burns in early October 2000, and given the temporary designation S/2000 S 2. It was named in August 2003 after a fictional shaman in the book The Curse of the Shaman, written by Michael Kusugak, who supplied Kavelaars with the names of giants from Inuit mythology that were used for... Read more on Wikipedia.
Wikidata