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How does Triton compare in size with Neptune’s other moons?

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Moons of Neptune: Triton — Triton Image of Triton, Neptune's largest satellite, captured by a camera aboard Voyager 2, 1989.

Triton is by far the largest of Neptune’s moons, standing as the only large satellite in the system. With a diameter of approximately 2,706.8 km, it is significantly larger than its siblings.12

To put its size into perspective:
* Proteus: Triton is more than six times the size of Proteus, which is the next largest moon in the system.1
* Nereid: Triton is substantially larger than Nereid, which has a diameter of about 340 km.2
* Other Moons: The remaining moons of Neptune are much smaller, with most having mean radii of less than 100 km.1

Triton’s scale is such that it is often compared to Earth’s Moon, which it approaches in diameter. Because of its size and unique orbital characteristics—such as its retrograde motion—astronomers believe Triton is a captured object that likely formed independently in the Kuiper belt before being pulled into Neptune’s orbit.132