delta-8-THC, naturally occurring chemical compound found in cannabis plants, namely the species Cannabis indica and C. sativa, which are sources of hemp and marijuana. Delta-8-tetrahydrocannabinol (THC) is chemically related to delta-9-THC, which is the primary psychoactive compound in cannabis products; delta-8-THC, however, has milder psychoactive effects. Delta-8-THC is thought to have some potential therapeutic benefits, though a lack of scientific evidence and regulatory oversight has raised concerns about safety and quality.

Delta-8-THC is so-named for the location of a double bond that occurs on the eighth carbon atom in its molecular carbon chain structure. The location of this bond is significant, since it not only is used to define the different types of THC but also affects the interaction of THC molecules with cellular receptors. Within cannabis plants, only very small amounts of delta-8-THC are produced, far less than delta-9-THC. Semisynthetic delta-8-THC can be produced from cannabidiol (CBD) that has been extracted from hemp or generated via isomerization of delta-9-THC. In general, delta-8-THC is more easily synthesized than delta-9-THC and its semisynthetic forms are more stable. Semisynthetic delta-8-THC is used in products such as capsules, gummies, vape cartridges, and tinctures. Because it has only partial efficacy at cannabinoid receptors, it is less potent than many synthetic cannabinoids.

Anecdotal reports suggest that delta-8-THC possesses potential health benefits. For example, some persons believe that the substance can reduce nausea, relieve chronic pain, and help reduce anxiety. Evidence for these claims, however, is largely lacking. Moreover, similar to other cannabinoids, delta-8-THC can cause side effects, including dry mouth, drowsiness, and fatigue. It also can impair coordination and judgment and increase anxiety. In addition, many delta-8-THC products are not tested for purity or safety, and research indicates that such products vary in cannabinoid content and potency. In fact, many products sold as delta-8-THC do not actually contain the compound in pure form and are contaminated with other cannabinoids, including delta-9-THC and chemically related substances not known to occur naturally. Various reaction by-products have also been detected in delta-8-THC products. These factors have raised significant concerns about product safety.

In addition, the legal status of delta-8-THC is complex. In the United States, for example, under the Agriculture Improvement Act of 2018, hemp-derived products with less than 0.3 percent THC are not controlled substances. However, because delta-8-THC is sometimes considered a type of synthetic cannabinoid, its legality is questioned and potentially subject to federal restrictions. Moreover, state laws differ, with some states allowing and others banning delta-8-THC. The legality of delta-8-THC is similarly ambiguous in other countries, particularly those of the European Union. Other countries have relatively clear laws, such as in Canada, where delta-8-THC is regulated as a controlled substance under the Cannabis Act.