Stephenson 2-18

Stephenson 2-18 (St2-18, also known as Stephenson 2-18 and RSGC2-18) is a red supergiant (RSG) or red hypergiant (RHG) star. It is close to, and a possible member of, the open cluster Stephenson 2. It is about 6,000 parsecs (20,000 ly) away from Earth in the constellation of Scutum and is one of the largest known stars.
It is also one of the most luminous of its type. It has a radius of 2,150 times that of the Sun, and has a volume 10 billion times that of the Sun.
This star has a spectral type of M6, which is pretty unusual for a supergiant star and corresponds to its cool temperature of 3,200 Kelvin. It can fit about 13 quadrillion Earths in it.