What is the name of the spacecraft that first visited Jupiter?

The spacecraft that first visited Jupiter was Pioneer 10.

Launched by NASA on March 3, 1972, Pioneer 10 was designed to travel beyond Mars, cross the asteroid belt, and investigate Jupiter. It reached the planet on December 3, 1973, passing about 132,252 kilometers above Jupiter’s cloud tops. The mission returned the first close-up images of Jupiter and important measurements of its magnetic field, radiation belts, atmosphere, and moons.

Pioneer 10 also achieved several other milestones. It was the first spacecraft to traverse the asteroid belt and the first to use a planetary flyby to gain speed and change its trajectory toward the outer Solar System. Its successor, Pioneer 11, visited Jupiter later and then became the first spacecraft to encounter Saturn.

A common mix-up is Voyager 1, which also visited Jupiter and produced spectacular images. Voyager 1 arrived in 1979, six years after Pioneer 10, so it was not the first spacecraft to reach the planet.