As of 2026-10-17, 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 was the second moon of Neptune to be discovered, by Gerard Kuiper in 1949. It is notable for its unusually eccentric orbit and relatively large size for an irregular satellite. Nereid also exhibits large brightness variations over long periods of time, the origin of which has yet to be conclusively explained. 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 Himalia — 170 km
moon of Jupiter
Himalia, also known as Jupiter VI, is the largest irregular satellite of Jupiter. With a diameter of around 140 km (90 mi), it is the sixth largest Jovian satellite, after the four Galilean moons and Amalthea. It was discovered by Charles Dillon Perrine at the Lick Observatory on 3 December 1904 and is named after the nymph Himalia, who bore three sons of Zeus. It is the largest member of the Himalia group, a group of moons that orbit in the prograde direction around Jupiter, likely a... Read more on Wikipedia.
Wikidata - #5 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 - #6 Halimede — 62,000 m
moon of Neptune
Halimede, also known as Neptune IX and previously as S/2002 N 1, is an irregular moon of Neptune. 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, Halimede follows a distant, highly eccentric, and highly inclined orbit with an average orbital period of about 5.1 Earth years. Like the majority of irregular moons, Halimede's... Read more on Wikipedia.
Wikidata - #7 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, 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 Sun—and... Read more on Wikipedia.
Wikidata - #8 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 - #9 Psamathe — 38,000 m
moon of Neptune
Psamathe, also known as Neptune X and previously as S/2003 N 1, is an irregular moon of Neptune. It was discovered by Scott Sheppard, David Jewitt, and Jan Kleyna at Mauna Kea Observatory on 29 August 2003. Named after one of the Nereids from Greek mythology, Psamathe follows a distant, highly eccentric, and highly inclined orbit with an average orbital period of about 25 Earth years. Like the majority of irregular moons, Psamathe's orbit is retrograde, meaning it revolves around Neptune in the... Read more on Wikipedia.
Wikidata - #10 Ananke — 29,100 m
moon of Jupiter
Ananke, also known as Jupiter XII, is a natural satellite or moon of Jupiter. It is one of Jupiter's irregular moons, which orbit far from the planet on highly inclined and eccentric orbits. Ananke was discovered by Seth Barnes Nicholson at Mount Wilson Observatory in 1951. Read more on Wikipedia.
Wikidata