Who was the Roman king of the gods?

The Roman king of the gods was Jupiter.

Jupiter was the chief deity of Roman state religion and ruled the sky and thunder. Romans associated him with sovereignty, law, oaths, and the authority of the state. His Greek counterpart was Zeus, and Roman writers often adapted Greek myths and imagery when describing Jupiter.

Jupiter’s symbols included the thunderbolt, eagle, and oak tree. His major temple, the Temple of Jupiter Optimus Maximus, stood on Rome’s Capitoline Hill. He formed the Capitoline Triad with Juno and Minerva, a trio central to Rome’s public religious life. The Romans also called him Jove, a name preserved in words such as “jovial.”

The other options represent different roles. Pluto ruled the underworld, Saturn was an older generation of god associated with agriculture and time, and Mars was the god of war. Jupiter’s planetary namesake is the largest planet in the Solar System, but the planet’s name ultimately comes from this Roman supreme deity.