What planet has the longest year? Astronomy Our Solar System The Planets 1 Answer chandramohanPanakkal Apr 29, 2017 Neptune. Explanation: 164.8 Earth years. Answer link Related questions What effect does Earth’s gravitational force have on objects of different masses? What solar system is Pluto in? Which planet in our solar system is most earth like? What is the closest planet to the sun? Why are the planets closest to the sun rocky? Why is earth closest to the sun in January? Why is Mars closest to the Earth in August? What is accretion, and how did it form the Earth? How does accretion explain planet formation? How does accretion form planets? See all questions in The Planets Impact of this question 4313 views around the world You can reuse this answer Creative Commons License