What are the four largest moons of Jupiter called?
They are also called the Galilean satellites or Galilean moons.
These four moons of Jupiter -- from innermost to outermost Io, Europa, Ganymede and Callisto --were discovered in 1610 by Galileo Galilei through telescopic observation. They are one of the first telescopic discoveries.
The Galilean moons are perhaps of greater interest than Jupiter itself, especially with respect to the possibility of life elsewhere.
Io is driven by powerful Jovian tides to consant volcanic activity, which drives out water and most other volatile compounds. This likely snuffs out life as we know it, and the same thing could happen to otherwise potentially Earthlike planets orbiting close to low luminosity stars.
In contrast, the other three Galilean moons have retained great quantities of water ice, and all likely have subterranean watery oceans that could harbor life themselves. In Europa this ocean is especially prominent.