As of July 2013, we know of fourteen moons orbiting Neptune.  The largest, Triton, was discovered only 17 days after Neptune itself was found in 1846 and it would be over a hundred years before any others were first seen.  Triton is one of the larger moons in the Solar System with a diameter of 2700km, and orbits backwards around Neptune.  The most recently discovered moon, by contrast, is less than 20km across, and is known as S/2004 S1, until the IAU votes on a proper name for it.