Pluto is about 3.67 billion miles from the Sun on average.
That distance equals roughly 39.44 astronomical units, with one astronomical unit being the average Earth–Sun distance. Pluto’s orbit is highly elliptical, so its actual distance changes substantially: it can come as close as about 30 AU and travel as far as roughly 49.3 AU from the Sun.
Pluto was discovered in 1930 and was long taught as the ninth planet. In 2006, the International Astronomical Union classified it as a dwarf planet because it has not cleared other objects from its orbital neighborhood. Its great distance also means sunlight takes about 5.5 hours to reach it.
A common mix-up is assuming Pluto is always the most distant major object in the solar system. Its orbit once brought it closer to the Sun than Neptune, from 1979 to 1999. Several dwarf planets, including Eris, are farther away on average.