The JPL-managed Juno spacecraft blasted off from Cape Canaveral, Fla.
Juno is solar powered with three huge panels, a first for a spacecraft intended to roam so far from the sun. The total mission costs $1.1 billion.
Scientists hope Juno will provide information about Jupiter's origins. The gas giant is believed to be the solar system's oldest planet.
Juno will spend at least one year circling Jupiter's poles.
Attached to Juno are three little Lego figures. They represent the Italian physicist Galileo, who discovered Jupiter's biggest moons; the Roman god Jupiter; and his wife Juno, for whom the spacecraft is named.
The Associated Press contributed to this report.