海底热泉（hydrothermal vent）亦作海底热液系统（Submarine Hydrothermal System），是从海底喷出经由地热加热过的水及其裂缝喷发口。通常发现于火山活动频发、大陆板块移动的地区及海盆、热点附近。常见陆地类型为温泉、火山喷气孔和间歇泉。在海底常会形成海底烟柱，相对于同样深度的其他海底地区，海底热泉附近通常生物更为繁盛，它们倚靠分解热泉中流出的矿物质为食。化能合成细菌和古生菌形成了此处食物链的最底层，支持着多样化生物，包括巨型管蠕虫、一些蛤蜊和节肢动物的生存。活跃的海底热泉还被认为存在于木星的卫星木卫二上，并且古代海底热泉被认为在火星上观察到。

A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both geologically active and has large amounts of water on its surface and within its crust. Common land types include hot springs, fumaroles and geysers. Under the sea, hydrothermal vents may form features called black smokers. Relative to the majority of the deep sea, the areas around submarine hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic bacteria and archaea form the base of the food chain, supporting diverse organisms, including giant tube worms, clams, limpets and shrimp. Active hydrothermal vents are believed to exist on Jupiter's moon Europa, and Saturn's moon Enceladus, and it is speculated that ancient hydrothermal vents once existed on Mars.