Phytocannabinoids are meroterpenoids biosynthesized in Cannabis sativa L. through the alkylation of alkylresorcinols with terpenoid moieties. Over 200 structurally diverse phytocannabinoids have been identified, showing wide variability in their isoprenyl substituents (monoterpenyl, sesquiterpenyl, cyclic or acyclic), alkyl chain length, and functionalization of the aromatic core (e.g., O-methylation, oxidation, or dimerization). This remarkable structural diversity originates from the orthogonal nature of their biosynthetic modifications, which underpin a wide range of biological activities. While Δ9-Tetrahydrocannabinol (Δ9-THC) has long been recognized for its psychotropic effects, increasing attention has turned to non-psychotropic phytocannabinoids such as cannabidiol (CBD), which exhibit anti-inflammatory, neuroprotective, anticonvulsant, and analgesic properties. These developments have opened up new avenues for therapy, including the treatment of refractory pediatric epilepsy, chronic pain, and spasticity associated with multiple sclerosis. The characterization of the endocannabinoid system in the 1990s, which includes endogenous ligands and specific cannabinoid receptors, has provided a biological framework for these effects. This chapter presents an updated overview of the chemically and biologically rich class of phytocannabinoids that are increasingly relevant in pharmacology.