The largest dwarf planet in our solar system is Eris. It is a bit larger than Pluto and has one known moon. Because it was larger than Pluto, astronomers decided to be classified as a planet. But, at that time, Pluto itself was under question of whether it should be classified a planet or a dwarf planet. Once Pluto was decided to be classified as a dwarf planet, Eris too was classified as one. Eris got its name from the Greek goddess, Eris who was the goddess of strife and discord.
Diameter: 2400 km (roughly the size of Pluto which is 2274 km.)