Serpentine soil is an uncommon soil type produced by weathered ultramafic rock such as peridotite and its metamorphic derivatives such as serpentinite. More precisely, serpentine soil contains minerals of the serpentine subgroup, especially antigorite, lizardite, and chrysotile or white asbestos, all of which are commonly found in ultramafic rocks. The term "serpentine" is commonly used to refer to both the soil type and the mineral group which forms its parent materials.

Serpentine soils exhibit distinct chemical and physical properties and are generally regarded as poor soils for agriculture. The soil is often reddish, brown, or gray in color due to its high iron and low organic content. Geologically, areas with serpentine bedrock are characteristically steep, rocky, and vulnerable to erosion, which causes many serpentine soils to be rather shallow. The shallow soils and sparse vegetation lead to elevated soil temperatures and dry conditions. Due to their ultramafic origin, serpentine soils also have a low calcium-to-magnesium ratio and have low levels of many essential nutrients such as nitrogen (N), phosphorus (P), and potassium (K). Serpentine soils contain high concentrations of heavy metals, including chromium, iron, cobalt, and nickel. Together, these factors create serious ecological challenges for plants living in serpentine soils.

Serpentinite is a meta-igneous rock formed by the metamorphic reaction of olivine-rich rock, peridotite, with water. Serpentinite has a mottled, greenish-gray, or bluish-gray color and is often waxy to the touch. The rock often contains white streaks of chrysotile running through it, which are a type of naturally occurring asbestos. Asbestos is linked to an array of human health conditions such as mesothelioma from long-time exposure of breathing in the dust particles. Caution should be taken when working in serpentine soils or when working with crushed serpentine rocks.

Serpentinite most often forms in oceanic crust near the surface of the earth, particularly where water circulates in cooling rock near mid-ocean ridges: masses of the resulting ultramafic rock are found in ophiolites incorporated in continental crust near present and past tectonic plate boundaries.

Serpentine soils are derived from ultramafic rocks. Ultramafic rocks are igneous or metamorphic rocks that contain more than 70% iron or magnesium minerals.

Serpentine soils are widely distributed on Earth, in part mirroring the distribution of ophiolites. There are outcroppings of serpentine soils in the Balkan Peninsula, Turkey, Newfoundland, the island of Cyprus, the Alps, Cuba, and New Caledonia. In North America, the majority of the serpentine soils are in California; however, serpentine is also present in small but widely distributed areas on the eastern slope of the Appalachian Mountains in the eastern United States.

Ecologically, serpentine soils have three main traits: poor plant productivity, high rates of endemism, and vegetation types that are distinct from neighboring areas.

Serpentine plant communities range from moist bogs and fens to rocky barrens and must be able to tolerate the harsh environmental conditions of such poor soil. As a result, they are often drastically different from non-serpentine soil areas bordering the serpentine soils. Vegetative characteristics are often shared among the types of flora found on serpentine soils. They will exhibit a "stunted" growth habit, with dull waxy, gray-green leaves (seen in Eriogonum libertini), which allow for water retention and sunlight reflection respectively. Other possible phenotypic traits include pigmented stems (as seen in the Streptanthus howellii) and occasionally a carnivorous nature as seen in the Darlingtonia californica. Some examples of common serpentine tolerant plants include gray pine (Pinus sabiniana), Jeffrey Pine (Pinus jeffreyi), California lilac (Ceanothus sp.), manzanita (Arctostaphylos sp.), live oak (Quercus sp.), California redbud (Cercis occidentalis), California buckeye (Aesculus californica), California laurel (bay tree) (Umbellularia californica), and the ferns Aspidotis densa and Polystichum lemmonii.