Outline of Neptune

The following outline is provided as an overview of and topical guide to Neptune:

Neptune – eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune.^[a] Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50×10⁹ km). It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident.

Classification of Neptune

Astronomical object
- Gravitationally rounded object
  - Planet
    - Giant planet
      - Ice giant
    - Planet of the Solar System
      - Outer planet
      - Superior planet

Location of Neptune

Milky Way Galaxy – barred spiral galaxy
- Orion Arm – a spiral arm of the Milky Way
  - Solar System – the Sun and the objects that orbit it, including 8 planets, the eighth and furthest planet from the Sun being Neptune
    - Orbit of Neptune