How many Earth days does it take for Venus to rotate once on its axis?

Venus takes about 243 Earth days to rotate once on its axis. This is its sidereal rotation period, measured relative to distant stars, and it is longer than Venus's 224.7-Earth-day trip around the Sun.

Venus rotates retrograde, meaning it spins in the opposite direction from most planets, including Earth. As a result, an observer able to see through the planet's opaque clouds would see the Sun rise in the west and set in the east. The slow spin may reflect a long-term balance among solar tides, gravitational effects, and atmospheric tides caused by the heating of Venus's massive atmosphere.

The 243-day figure is often confused with Venus's solar day, the interval from one sunrise to the next. Because retrograde rotation combines with Venus's orbit around the Sun, a solar day lasts only about 116.75 Earth days. That is why 116.8 days is a plausible neighboring fact, but it does not answer how long Venus takes to rotate once relative to the stars.

Venus's long rotation period also fluctuates slightly because its dense atmosphere exchanges angular momentum with the solid planet. Its atmosphere, meanwhile, races around the planet in only about four Earth days at cloud level, a phenomenon called atmospheric super-rotation.