Which planet has the strongest magnetic field?

Jupiter has the strongest magnetic field of any planet in the Solar System. Its field is roughly an order of magnitude stronger than Earth's near the planet and creates the largest planetary magnetosphere known in the Solar System.

The field is generated by a dynamo deep inside Jupiter, where circulating liquid metallic hydrogen conducts electricity. Jupiter's rapid rotation helps organize and intensify this field. Its magnetic influence extends far beyond the planet, forming a huge magnetosphere that is compressed on the Sun-facing side and stretched into a long magnetotail on the opposite side.

Jupiter's moon Io makes the magnetosphere even more dynamic. Io's volcanoes release material that becomes ionized and forms a plasma torus around Jupiter. The planet's magnetic field forces this plasma to co-rotate, producing intense radiation belts and powerful auroras. Jupiter's magnetic field was first directly measured during the Pioneer 10 flyby in 1973. Earth also has a protective magnetosphere, but Jupiter's is vastly stronger and larger.