The planet with the most eccentric orbit is Mercury. Its orbit has an eccentricity of about 0.2056, making it the most elliptical compared to the orbits of other planets in the Solar System. This eccentricity causes significant variations in Mercury's distance from the Sun, leading to extreme temperature fluctuations. The planet's proximity to the Sun and its quick orbit contribute to this phenomenon, as it completes a revolution in just 88 Earth days. Mercury's unique orbit results in unusual solar days and an intriguing climate, which differs notably from the more circular trajectories of the other planets.