The planet Venus was at one time the most volcanically active planet in the solar system. Its surface is strewn with both large and small volcanoes, and some of the volcanic processes that seem to have occurred on the planet are unlike any known on Earth.
Venus has at least 1,600 major volcanoes. The number of minor volcanoes has never been accurately tallied, but could range from 100,000 to over 1,000,000. Many of the large volcano types on Venus are familiar from Earth's geology. These include large shield volcanoes, which are formed from the gradual ooze of lava, and taller cone volcanoes with steep sides. The planet also has highly unusual volcanic structures, such as "pancake" volcanoes that are markedly flattened circles without a known equivalent anywhere else in the solar system.
It is not certain that Venus currently has active volcanoes, though there is some evidence that it does. In 1978 a section of Venus' northern hemisphere temporarily brightened, leading some astronomers to believe a large volcano was erupting there. During its 1989-1994 mission, the Magellan probe tested Venus' atmosphere and found a number of typically volcanic gases present in unusually high concentrations, which suggests that volcanic activity may have occurred not long before that time.