The planet with the largest moons is Jupiter. Among its many moons, Ganymede stands out as the largest, even exceeding the size of the planet Mercury. Jupiter has a total of 79 known moons, which vary widely in size, composition, and geological activity. Apart from Ganymede, other significant moons include Europa, known for its icy surface and potential subsurface ocean, and Io, famous for its volcanic activity. The study of these moons provides valuable insights into the formation of the solar system and the potential for life beyond Earth, making Jupiter a significant focus of astronomical research.