This illustration shows the approximate size of the red supergiant UY Scuti compared to the Sun.
UY Scuti is a bright red supergiant and pulsating variable star in the constellation Scutum. It is a current and leading candidate for being the largest known star by radius and is also one of the most luminous of its kind. It has an estimated radius of 1,708 solar radii; thus a volume nearly 5 billion times that of the Sun. It is approximately 2.9 kiloparsecs (9,500 light-years) from Earth. If placed at the center of the Solar System, its photosphere would at least engulf the orbit of Jupiter.
Image credit: Philip Park / CC BY-SA 3.0