Which planet is sometimes called the 'king of the planets'?

Jupiter is sometimes called the “king of the planets.”

The nickname is an informal description rather than an official astronomical title. It reflects Jupiter’s status as the largest planet in the Solar System, with more mass than all the other planets combined—about 2.5 times their total mass.

Jupiter’s “royal” reputation also has cultural roots. The planet is named after Jupiter, the chief god of ancient Roman religion, whose Greek counterpart is Zeus. In mythology, Jupiter was king of the gods, so the planetary nickname echoes both the world’s physical dominance and its name’s mythological origin.

The title should not be confused with a scientific classification. Jupiter is a gas giant, not a monarch, and Saturn, Uranus, and Neptune are also giant planets. Jupiter stands out because of its enormous size, powerful magnetic field, bright appearance, rapid rotation, and extensive moon system, including the four Galilean moons.