While no planet's orbit is perfectly circular, Venus has the lowest eccentricity (a measure of how much an orbit deviates from a perfect circle) of all the planets in our solar system.

Here's why:

* Low Eccentricity: Venus has an eccentricity of only 0.0068, which means its orbit is very close to a perfect circle.

* Other Planets: Most other planets have slightly more eccentric orbits, with Mars having the most elliptical orbit among the major planets.

It's important to remember that even though Venus has the roundest orbit, it's still not perfectly circular. All planets have slightly elliptical orbits due to gravitational influences from other celestial bodies.