NML Cygni or V1489 Cygni is a red hypergiant star. It is one of the largest stars known at present. It is about 1,640 times the Sun's radius, However an older study from 2010 says it is 1,183 solar radii. It is one of the extremely luminous supergiant stars. It was discovered in 1965, by Gerry Neugebauer, D.M. Martz and Robert Leighton. The name 'NML' comes from the names of the three discoverers. 