The largest object in the Solar System is the Sun. It is a star, and it makes up 99.8% of the mass of the Solar System. The Sun is so large that it could fit over 1 million Earths inside it.

Here is a comparison of the sizes of the Sun and some other celestial bodies:

* The Sun: 1.4 million km in diameter

* Jupiter: 142,984 km in diameter

* Saturn: 120,536 km in diameter

* Earth: 12,742 km in diameter

* Venus: 12,104 km in diameter

* Mars: 6,792 km in diameter

* Mercury: 4,879 km in diameter

As you can see, the Sun is much larger than any other object in the Solar System. In fact, it is so large that it could fit all of the other planets, moons, asteroids, and comets in the Solar System inside it with room to spare.

The Sun's size is also responsible for its immense gravity. This gravity is what keeps the planets in orbit around the Sun and prevents them from flying away into space.