10 Lacertae (10 Lac) is a star in the constellation Lacerta. Its apparent magnitude is 4.88. Located around 529 parsecs (1,730 ly) distant, it is a hot blue main-sequence star of spectral type O9V, a massive star that is currently fusing its core hydrogen. 10 Lacertae was one of the first O-type stars (along with S Monocerotis) to be defined as an anchor point for the MKK spectral classification; since the early twentieth century it has served as such a point. Specifically, the star is representative of O9V stars, meaning relatively cool O-type stars on the main-sequence.