Precious coral, or red coral, is the common name given to a genus of marine corals, Corallium. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink-orange skeleton, which is used for making jewelry.

Red corals grow on rocky seabottom with low sedimentation, typically in dark environments—either in the depths or in dark caverns or crevices. The first species to be described, C. rubrum (formerly Gorgonia nobilis), is found mainly in the Mediterranean Sea. It grows at depths from 10 to 300 meters below sea level, although the shallower of these habitats have been largely depleted by harvesting. In the underwater caves of Alghero, Sardinia (the "Coral Riviera"), it grows at depth from 4 to 35 meters. The same species is also found at Atlantic sites near the Strait of Gibraltar, at the Cape Verde Islands and off the coast of southern Portugal. Other Corallium species are native to the western Pacific, notably around Japan and Taiwan; these occur at depths of 350 to 1500 meters below sea level in areas with strong currents.

In common with other Octocorallia, red corals have the shape of small leafless bushes and grow up to a meter in height. Their valuable skeleton is composed of intermeshed spicules of hard calcium carbonate, colored in shades of red by carotenoid pigments. In living specimens, the skeletal branches are overlaid with soft bright red integument, from which numerous retractable white polyps protrude. The polyps exhibit octameric radial symmetry.

The following are known species in the genus:

The hard skeleton of red coral branches is naturally matte, but can be polished to a glassy shine. It exhibits a range of warm reddish pink colors from pale pink to deep red; the word coral is also used to name such colors. Owing to its intense and permanent coloration and glossiness, precious coral skeletons have been harvested since antiquity for decorative use. Coral jewellery has been found in ancient Egyptian and prehistoric European burials, and continues to be made to the present day. It was especially popular during the Victorian age.

Precious coral has hardness 3.5 on the Mohs scale. Due to its softness and opacity, coral is usually cut en cabochon, or used to make beads.

At the beginning of the 1st millennium, there was significant trade in coral between the Mediterranean and India, where it was highly prized as a substance believed to be endowed with mysterious sacred properties. Pliny the Elder remarks that, before the great demand from India, the Gauls used it for the ornamentation of their weapons and helmets; but by this period, so great was the Eastern demand, that it was very rarely seen even in the regions which produced it. Among the Romans, branches of coral were hung around children's necks to preserve them from danger from the outside, and the substance had many medicinal virtues attributed to it. The belief in coral's potency as a charm continued throughout the Middle Ages and early in 20th century Italy, where it is known as cerasuolo, it was worn as a protection from the evil eye and by women as a cure for infertility.

From the Middle Ages onward, the securing of the right to the coral fisheries off the African coasts was the object of considerable rivalry among the Mediterranean communities of Europe.