Styx, formerly S/2012 (134340) 1, S/2012 P 1, unofficially P5 is the fifth and last satellite of Pluto discovered, closest out of the small ones, also the smallest one. It was discovered by Mark Showalter on 9 images by Hubble Space Telescope taken on 26, 27, 29 June, 7, 9 July 2012. First images of Styx and Kerberos were taken by New Horizons best camera between 25 April and 1 May 2015.

It was initially thought to be between 10 and 25 kilometers in size, New Horizons estimated it at 7x5 kilometers, later corrected to 16x9x8

Styx spins around Pluto and Charon's barycentre between Charon and Nix orbits. Its semi-major axis is 42 656 km. It completes one rotation every 20.16655 days, being in orbital resonance with Hydra (11:6) and Nix (11:9), also being close to 1:3 resonance with Charon.

There was a poll where people could vote on its and another satellite's name, and the variants Vulcan and Kerberos won, however Styx got the name Styx and not Vulcan on 2 July 2013 because Vulcan had no relation to the dead realm.

Details on Styx surface will be named after river-related gods.

Pluto * Charon * Nix * Hydra * Kerberos * Styx