Neptune is an ice giant planet, one of two ice‑giant worlds in our Solar System (the other being Uranus).

What “ice giant” means

  • Ice giants are a subclass of giant planets that are smaller and denser than the gas‑giant pair Jupiter and Saturn.
  • They contain a higher proportion of “ices” such as water, ammonia, and methane, mixed with rock and a smaller fraction of hydrogen and helium in their interiors.

How Neptune differs from gas giants

  • Like Jupiter and Saturn, Neptune has a thick atmosphere dominated by hydrogen and helium, but it is much richer in volatiles (ices) than those two.
  • Compared directly with Uranus, Neptune is slightly smaller in size but more massive and denser, which is why both are placed in the “ice‑giant” category.

Snapshot in a table

Feature| Neptune (ice giant) 137
---|---
Type| Ice giant
Size (diameter)| About 4 times Earth’s diameter
Mass| Roughly 17 times Earth’s mass
Distance from Sun| About 4.5 billion km (30 AU)
Atmosphere main ingredients| Hydrogen, helium, plus significant methane and other ices
Color| Blue‑tinted due to methane in the upper atmosphere 36

So, in short: Neptune is an ice‑giant planet , not a rocky world like Earth, nor a classic gas giant like Jupiter.