Venus is the second planet from the Sun and the only terrestrial object in the Solar System other than Earth that has a substantial atmosphere and is almost as massive and large as Earth. Like Mercury, Venus orbits the Sun always closer than Earth, resulting in it appearing in Earth's sky always inferior (close to the Sun) and at night as either a "morning star" or "evening star". Venus appears in Earth's sky also as the brightest natural object, aside from the Sun and Moon, due to its proximity to Earth and the Sun, its large size and high albedo. These prominent appearances of Venus in Earth's sky have made Venus a common and important object for humans, their cultures and astronomy.

Venus has a weak induced magnetosphere, but retains a thick atmosphere of mainly carbon dioxide, which creats a strong greenhouse effect. This results in an intense mean temperature of 737 K (464 °C; 867 °F) at the bottom of the atmosphere, where the thick atmosphere reaches an 92 times higher atmospheric pressure than Earth has at its surface, turning the air into a supercritical fluid. At the bottom of the atmosphere lies a terrestrial surface of volcanic origin. Water might have formed oceans on Venus before runaway greenhouse effects increased the atmospheric temperature, evaporating the water, which subsequently also dissapeared from the atmosphere. The atmosphere obscures the surface of Venus, as it has the highest albedo in the Solar System, and sulfuric acid clouds cover the planet. The possibility of life on Venus has long been a topic of speculation, particularly in the clouds of Venus, featuring layers of more Earth-like conditions at roughly 50 km altitude, but despite recent indicative research, no convincing evidence has been found thus far.

Venus is a planet without a moon (like Mercury), and rotates (like Uranus) in a retrograde direction, meaning against its orbital motion, making the Sun in the sky of Venus move from its west to its east. With Venus' rotation being slowed by its strong atmospheric currents, to a sidereal rotation period of 243 Earth days, the longest of all the planets of the Solar System, and combined with rotating in a retrograde direction, solar days on Venus have a length of 117 Earth days, just about half as long as it takes Venus to go around the Sun, having a solar year of 224.7 Earth days.

While Mercury comes more frequently close to Earth as well as Venus, the orbit of Venus and Earth is closest to each other, being the closest orbits of any other pairs of planets in the Solar System. This orbital proximity of Venus and Earth results in the lowest gravitational potential difference and lowest delta-v needed for orbital transfer between them, than to any other planet. This has allowed Venus to be the most accessible destination and gravity assist waypoint for interplanetary missions, having inferior conjunctions with a synodic period of 1.6 years. In 1961 Venus became the target of the first interplanetary flight in human history, followed by the first probes to report from another planet, enter one's atmosphere and land on one. Crewed missions to Venus have been proposed particularly as part of crewed missions to Mars, but also as missions to enter and stay in the atmosphere of Venus, at cloud levels with Earth-like pressure, temperature, radiation and gravitation.