Earth is the third planet from The Sun in The Solar System and the only known celestial body to support life. With a radius of approximately 6,371 kilometers (3,959 miles) and an estimated age of around 4.54 billion years, Earth is unique in its combination of conditions that foster a wide range of ecosystems. It has a diverse range of biomes, from tropical rainforests to arid deserts and icy tundras, supporting an astonishing variety of plant and animal species. The planet is composed of a solid iron-nickel core, a molten outer core, a mantle, and a thin outer crust. Its atmosphere contains roughly 78% nitrogen, 21% oxygen, and trace amounts of other gases, including carbon dioxide and water vapor, making it breathable for most terrestrial life forms.

Earth's axial tilt and orbit around the Sun result in the changing seasons and a relatively stable climate, although human activities, particularly the emission of greenhouse gases, have begun to noticeably impact this climate. Oceans cover about 71% of the Earth's surface, playing a critical role in regulating temperature and weather patterns. The planet is divided into seven continents: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Human civilization has developed over millennia, with recorded history spanning roughly 5,000 years. Various cultures, religions, and philosophies have emerged, enriching the collective human experience. Scientific understanding of Earth has evolved significantly over time, from early geocentric models to the current understanding provided by fields like geology, meteorology, and environmental science. Earth is also explored in the context of the wider universe through the disciplines of astronomy and space science, highlighting its unique status as the only known planet to harbor life.