Here's why:

* Mass: Jupiter is the largest planet in our solar system, with a mass that's over 300 times greater than Earth's. Gravity is directly proportional to mass, meaning the more massive an object is, the stronger its gravitational pull.

* Density: While Jupiter is a gas giant, it's still incredibly dense due to the immense pressure at its core. This density contributes to its strong gravity.

Important Note: While Jupiter has the strongest gravity amongst the planets in our solar system, it's still significantly weaker than the Sun's gravity. The Sun's immense mass holds all the planets in our solar system in orbit.