The planet with the largest elliptical orbit in our solar system is Mercury.

Here's why:

* Eccentricity: Eccentricity is a measure of how much an orbit deviates from a perfect circle. A value of 0 means a perfectly circular orbit, while a value of 1 represents a highly elongated ellipse.

* Mercury's Eccentricity: Mercury has an eccentricity of 0.206, which is the highest of any planet in our solar system. This means its orbit is significantly more elliptical than the orbits of the other planets.

This high eccentricity leads to significant variations in Mercury's distance from the Sun throughout its orbit.