UY Scuti is a red supergiant star in the Scutum constellation. It is currently the largest known star with a diameter of 2,375,828,000 kilometres. That means it would take 2.2 hours to cross it’s diameter at the speed of light.
It has a volume approximately 5 billion times that of the Sun, and if placed in the middle of the solar system UY Scuti would engulf all the planets all the way to Jupiter, filling more than halfway through Saturn’s orbit.