Which celestial body in our solar system has the most mass?

Jupiter has the largest mass.

"Weight" is the mutual force of gravity between two masses. The "weight" of a single mass,

remote from any others, has no meaning.

At its surface, Jupiter has the greatest gravitational acceleration of any planet in the solar system.

But its "weight" depends on what other mass you place near it, and exactly how far apart they are.

If I am the other mass, and I place myself 44,423 miles from the center of Jupiter, at its "surface",

then in my gravitational field, Jupiter weighs roughly 448 pounds.