Ginsenosides or panaxosides are a class of natural product steroid glycosides and triterpene saponins. Compounds in this family are found almost exclusively in the plant genus Panax (ginseng), which has a long history of use in traditional medicine that has led to the study of pharmacological effects of ginseng compounds. As a class, ginsenosides exhibit a large variety of subtle and difficult-to-characterize biological effects when studied in isolation.

Ginsenosides can be isolated from various parts of the plant, though typically from the roots, and can be purified by column chromatography. The chemical profiles of Panax species are distinct; although Asian ginseng, Panax ginseng, has been most widely studied due to its use in traditional Chinese medicine, there are ginsenosides unique to American ginseng (Panax quinquefolius) and Japanese ginseng (Panax japonicus). Ginsenoside content also varies significantly due to environmental effects. The leaves and stems have emerged as a more abundant and easier-to-extract source of ginsenosides. Ginsenosides have also been found in jiaogulan, making jiaogulan the first plant outside of Araliaceae to contain ginsenosides.

Ginsenosides are named according to their retention factor in thin layer chromatography (TLC). The letter or number after R is a serial indication of the retention factor, with '0' being most polar, followed by 'a' for the second-most polar, to 'h' being a fairly non-polar ginsenoside. Some of these groups turn out to consist of several molecules are further broken down with numbers: for example, Ra1 is more polar than Ra2. Terms such as "20-gluco-f" may be used to indicate further modification.

A different nomenclature is applied to so-called pseudoginsenosides and notoginsenosides. The difference in name reflects more about the circumstances of their discovery than about their chemical nature.

They can be broadly divided into two groups based on the carbon skeletons of their aglycones: the four-ring dammarane family, which contains the majority of known ginsenosides, and the oleanane family. The dammaranes further subdivided into 2 main groups, the protopanaxadiols (PPDs) and protopanaxatriols (PPTs), with other smaller groups such as the ocotillol-type pseudoginsenoside F11 and its derivatives.

To each ginsenoside is bound at least 2 or 3 hydroxyl groups at the carbon-3 and -20 positions or the carbon-3, -6, and -20 positions respectively. In protopanaxadiols, sugar groups attach to the 3-position of the carbon skeleton, while in comparison sugar groups attach to the carbon-6 position in protopanaxatriols. Well known protopanaxadiols include Rb1, Rb2, Rc, Rd, Rg3, Rh2, and Rh3. Well known protopanaxatriols include Re, Rg1, Rg2, and Rh1.

Ginsenosides that are a member of the oleanane family are pentacyclic, composed of a five ring carbon skeleton. R0 (also written Ro) is an example.

The biosynthetic pathway of ginsenosides start in a way common to most steroids, from squalene to 2,3-oxidosqualene via the action of squalene epoxidase, at which point dammaranes can be synthesized through dammarenediol synthase and oleananes through beta-amyrin synthase. As of 2021, the full conversion pathway to protopanaxadiol, protopanaxatriol, and oleanolic acid are known with each step having been assigned at least one gene. Ootillol synthesis remains unclear: 2,3-oxidosqualene is believed to first be converted into 2,3,22,23-dioxidosqualene. An unknown oxidosqualene cyclase produces 3-epicabraleadiol, which is the immediate precursor to ootillol.