How many moons does Pluto have?

Pluto has four known moons. Charon, the largest one, Hydra and Nix, both very small. Charon was discovered in 1978, and Nix/Hydra were identified in 2005.

In 2011 a new moon was identified called P4 or S/2011 (134340) 1 [See related link BBC]

The largest, Charon, is proportionally larger, compared to its primary, than any other satellite of a known planet or dwarf planet in the solar system.

In fact there is some discussion as to whether we should consider this a "binary system" instead of a dwarf planet with moons because Charon is so massive that the barycenter (center of gravity around which the bodies rotate) of the Pluto-Charon group is not inside either of those bodies.