The planet with the most oxygen is Earth.
While other planets and moons in our solar system have traces of oxygen, Earth is the only one with a significant atmosphere composed primarily of oxygen. Oxygen makes up about 21% of Earth's atmosphere, which is essential for life as we know it. This abundance of oxygen is due to billions of years of photosynthesis by plants and algae.
It's important to note that oxygen levels on other planets can vary greatly depending on factors like atmospheric composition, geological activity, and the presence of life.
For example, Mars has a very thin atmosphere with only trace amounts of oxygen. While Venus has a dense atmosphere, it's primarily composed of carbon dioxide, with only a tiny fraction of oxygen.