Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet, being orbital neighbours as well as Venus having the most similar mass and size to Earth among the planets of the Solar System. While both are rocky planets, Venus has an atmosphere much thicker and denser than Earth and any other rocky body in the Solar System. Its atmosphere is composed of mostly carbon dioxide (CO2), with a global sulfuric acid cloud cover and no liquid water. At the mean surface level the atmosphere reaches a temperature of 737 K (464 °C; 867 °F) and a pressure 92 times greater than Earth's at sea level, turning the lowest layer of the carbon dioxide atmosphere into a supercritical fluid.
Venus is the third brightest object in Earth's sky, after the Moon and the Sun, and, like Mercury, always appears relatively close to the Sun, either as a "morning star" or an "evening star", resulting from orbiting closer (inferior) to the Sun than Earth. Venus has no moons.
Venus is the destination from Earth, compared to the other planets, with the lowest delta-v needed to reach it, and is therefore often used for gravity assists and as a common waypoint for interplanetary flights from Earth. While the orbit of Venus is the next closest to Earth's, Venus and Earth stay on average the second closest planets to each other, with only the most inferior orbiting Mercury staying closer to them and all the other Solar System planets. Venus and Earth approach each other in synodic periods of 1.6 years. Venus has a very slow retrograde rotation about its axis, a result of competing forces of solar tidal locking and differential heating of Venus's massive atmosphere. A Venusian day is 116.75 Earth days long, about half a Venusian solar year, which is 224.7 Earth days long.
Venus has a weak magnetosphere, lacking an internal dynamo it is induced by the solar wind and the atmosphere interacting.
Internally, Venus has a core, mantle, and crust. Internal heat escapes through active volcanism, resulting in resurfacing instead of plate tectonics. Venus may have had liquid surface water early in its history with a habitable environment, before a runaway greenhouse effect evaporated any water and turned Venus into its present state. Conditions at the cloud layer of Venus have been identified as possibly favourable for life on Venus, with possible biomarkers having been found in 2020, which has spurred new research and missions to Venus.
Throughout human history, Venus has been ascribed particular importance in the mythology, astrology, and fiction of various cultures across the world. The planet's characteristics ultimately proved crucial for the development of astronomy. The first telescopic observations of Venus in 1610 crucially proved the heliocentric model. In 1961 Venus was for the first time visited by a spacecraft (Venera 1), as a result of the very first interplanetary flight, but only the next interplanetary spacecraft, a year later, returned data (Mariner 2). Furthermore in 1967 the first atmospheric entry (Venera 4) and in 1970 the first soft landing (Venera 7) took place, the first on another planet than Earth. The study of Venus has informed the understanding of the greenhouse effect, global warming and climate change on Earth. As of 2025 the only active probe set to return to Venus is the Solar Orbiter performing flybys until 2030. The next planned Venus mission, the Venus Life Finder is expected to launch not earlier than summer 2026.
