Hashish, commonly shortened to hash, is an oleoresin made by compressing and processing parts of the cannabis plant, typically focusing on flowering buds containing the most trichomes. It is consumed as a psychoactive drug by smoking, typically in a pipe, bong, vaporizer or joint, or via oral ingestion. Hashish has a long history of usage in countries such as Afghanistan, Morocco, Egypt, Pakistan, India, Nepal, Iran, and Lebanon. Hashish consumption is also popular in Europe. In the United States, dried flowers or concentrates are more popular, and hash has seen a relative decrease in popularity following changes in laws that have indirectly allowed for the development and increased availability of cannabis extracts that are more potent than traditional hashish, although regional differences in product preferences exist. Like many recreational drugs, multiple synonyms and alternative names for hashish exist, and vary greatly depending on the country and native language.

Cannabis is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: Cannabis sativa, C. indica, and C. ruderalis. Alternatively, C. ruderalis may be included within C. sativa, all three may be treated as subspecies of C. sativa, or C. sativa may be accepted as a single undivided species. The genus is widely accepted as being indigenous to and originating from Asia.