A karst spring or karstic spring is a spring (exsurgence, outflow of groundwater) that is part of a karst hydrological system.

Because of their often conical or inverted bowl shape, karst springs are also known in German-speaking lands as a Topf ("pot") which is reflected in names such as Aachtopf (the source of the Radolfzeller Aach) or Blautopf (the source of the Blau river in Blaubeuren).

Karst springs often have a very high yield or discharge rate, because they are often fed by underground drainage from a large catchment basin. Because the springs are usually the terminus of a cave drainage system at the place where a river cave reaches the Earth's surface, it is often possible to enter the caves from karst springs for exploration.

Large karst springs are located in many parts of the world; the largest ones are believed to be in Papua New Guinea, with others located in Mediterranean countries such as Bosnia and Herzegovina, Croatia, Turkey, Slovenia, and Italy.

An estavelle or inversac is a ground orifice which, depending on weather conditions and season, can serve either as a sink or as a source of fresh water. It is a type of sinkhole.

A Vauclusian spring is a spring that originates from a shaft or a cave system, with the water surging upwards under relatively high pressure. It is named after the Fontaine de Vaucluse in southern France.

Submarine karst springs, also known as vruljas, occur worldwide, and are most numerous in shallow waters of the Mediterranean Sea. They can be considered to be karst springs which have become submerged by rising sea levels.

For intermittent or rhythmic springs see below. They are part of another type of classification, which differentiates between perennial (with continuous flow), rhythmic, and temporary springs.^{[clarification needed]}