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The effect of volcanic activity on submarine hydrothermal systems has been well documented along fast‐ and intermediate‐spreading centers but not from slow‐spreading ridges. Indeed, volcanic eruptions are expected to be rare on slow‐spreading axes. Here we report the presence of hydrothermal venting associated with extremely fresh lava flows at an elevated, apparently magmatically robust segment center on the slow‐spreading southern Mid‐Atlantic Ridge near 5°S. Three high‐temperature vent fields have been recognized so far over a strike length of less than 2 km with two fields venting phase‐separated, vapor‐type fluids. Exit temperatures at one of the fields reach up to 407°C, at conditions of the critical point of seawater, the highest temperatures ever recorded from the seafloor. Fluid and vent field characteristics show a large variability between the vent fields, a variation that is not expected within such …