Luminous Blue Variables (LBVs) are a class of very massive and luminous stars. They are known for sporadically ejecting a lot of matter, likely due to instabilities in their outer layers caused by strong radiation pressure from the core, and are often found in the conjunction with planetary nebulae. They are generally found near the upper luminosity limit of the Hertzsprung-Russell diagram, and most are believed to have evolved from stars with initial masses exceeding 40 times the mass of our Sun.

LBVs exhibit different types of variations occuring on a wide range of timescales. The largest variantions are associated with sudden increase in brightness by more than 3 magnitudes, lasting for several hundreds, maybe even several thousand years. The smallest known variations, sometimes less than 0.5 mag, last from several months, and up to several years.

Examples of LBVs are Eta Carinae, AG Carinae, P Cygni and S Doradus.