what planet is the largest in the universe
, Science writer, astronomy and planetary science. Biggest can be categorized into two -- largest (in diameter) or most massive (in mass). The largest confirmed planet in size, as of March 2015, is the WASP 17b. The planet is almost twice the size of Jupiter, but only half the mass. It is a gas giant and orbits very close to its host star, at about half the distance between Mercury and the Sun.