Cassini was the first spacecraft to orbit Saturn, entering orbit around the planet on 1 July 2004.
NASA, the European Space Agency, and the Italian Space Agency developed the Cassini-Huygens mission. The Cassini orbiter spent more than 13 years studying Saturn, its rings, magnetosphere, and moons. It made repeated close passes of Titan and discovered important evidence about the ocean beneath Enceladus’s icy surface.
The Huygens lander separated from Cassini and descended through Titan’s atmosphere, reaching the surface in January 2005. Cassini itself remained in orbit until its planned destruction in Saturn’s atmosphere on 15 September 2017.
Galileo orbited Jupiter, not Saturn. Voyager 1 and Voyager 2 flew past Saturn but did not enter orbit, making Cassini the first Saturn orbiter.