If you're counting dwarf planets than its eris. If not, than Neptune.
Neptune takes the longest as it is the farthest away.
Technically, since Pluto is no longer a planet, but a dwarf planet, Uranus is the planet that takes the longest to orbit the sun.
As it's the furthest planet out, Neptune takes the longest to orbit our sun, taking some 165 years to do so.
Neptune.
Neptune is the furthest planet from the sun, taking the longest time to complete one orbit, 164.79 years in total.
Mars takes the longest of the inner planets.
Neptune takes the longest as it is the farthest away.
If you still consider Pluto a planet, than Pluto takes the longest time to move around the sun. If not, Neptune takes the longest amount of time.
Neptune takes the longest to revolve around the sun.
Pluto
Technically, since Pluto is no longer a planet, but a dwarf planet, Uranus is the planet that takes the longest to orbit the sun.
Neptune does and it takes 164.8 years to do so.
Uranus
As it's the furthest planet out, Neptune takes the longest to orbit our sun, taking some 165 years to do so.
pluto has the longest year it takes 248 earth years in one revalution
Approxiamtely 6756313285.666678487m
Neptune.