The only planet in our solar system that is not named after a figure from Greek or Roman mythology is the planet Uranus.
Uranus is the seventh planet from the Sun and was discovered by William Herschel in 1781. When Herschel first proposed the name for the planet, he initially suggested calling it "Georgium Sidus" (Latin for "George's Star") in honor of King George III of England. However, this name did not gain widespread acceptance outside of Britain.
Eventually, the name Uranus was chosen, inspired by the Greek god of the sky, Uranus (Ouranos). While the name Uranus does have a mythological origin, it is not directly derived from Greek or Roman mythology like the names of the other planets in our solar system. Instead, Uranus is based on an ancient Greek deity associated with the sky.