The most distant planet in our solar system is Neptune. It is the eighth planet from the Sun, situated at an average distance of about 4.5 billion kilometers (2.8 billion miles).
However, there is a dwarf planet, Eris, which is located farther than Neptune, but it is not classified as a planet. Eris orbits the Sun at a greater average distance than Neptune, but its orbit is not as consistent—Eris has a highly elliptical orbit that takes it both closer to the Sun than Pluto at times and farther than Neptune at other times.
So, in terms of planets, Neptune holds the title as the most distant.