Mercury has the shortest orbit of any of the planets in the solar system. Because it is the closest planet to the sun, its orbit takes only 88 days.
In comparison to Mercury's 88-day orbit, Earth takes 365 days to orbit and Venus' orbit lasts 224 days. One year on Mars lasts 687 days, and Saturn's year is more than 29 Earth years long.
Neptune has the longest orbit of any planet in the solar system. It takes almost 165 Earth years for it to orbit the sun once, so no one has lived long enough to see Neptune complete a full orbit. Before Pluto lost its planet status, it was the planet with the longest orbit, at 248 Earth years.