UY Scuti

UY Scuti is a red supergiant. It was the largest star ever discovered.

Properties
Though it was discovered long ago, we only recently discovered it's tremendous size! In 2012, it, along with KW Sagittarii and AH Scorpii were determined to be at least 1,000 times wider than the Sun. We eventually found out that it was 916 times wider than the Sun.