Hashish (Arabic: حشيش, (IPA: [ħæʃiːʃ])), also known as hash, "dry herb, hay" is a drug made by compressing and processing parts of the cannabis plant, typically focusing on flowering buds (female flowers) containing the most trichomes. It is consumed by smoking, typically in a pipe, bong, vaporizer or joint, or via oral ingestion. Hash has a long history of usage in countries such as Morocco, Egypt, Afghanistan, Pakistan, India, Nepal, Iran, and Lebanon. Hash consumption is also popular in Europe. In the United States, dried flowers or concentrates are more popular, though hash has seen a rise in popularity following changes in law. Like many recreational drugs, multiple synonyms and alternative names for hash exist, and vary greatly depending on the country and native language.

Hash is a cannabis concentrate product composed of compressed or purified preparations of stalked resin glands, called trichomes, from the plant. It is defined by the 1961 UN Single Convention on Narcotic Drugs (Schedule I and IV) as "the separated resin, whether crude or purified, obtained from the cannabis plant". The resin contains ingredients such as tetrahydrocannabinol (THC) and other cannabinoids—but often in higher concentrations than the unsifted or unprocessed cannabis flower. Purities of confiscated hashish in Europe (2011) range between 3% and 15%. Between 2000 and 2005, the percentage of hashish in cannabis end product seizures was at 18%. With the strength of unprocessed cannabis flowers having increased greatly in recent years—with flowers containing upwards of 25% THC by weight—the strength of hashish produced today and in the future is likely to be far more potent than in these older records.

The consistency and appearance of hash vary depending on the process and amount of leftover plant material (e.g. chlorophyll). It is typically solid, though its consistency ranges from brittle to malleable. It is most commonly light or dark brown in color, though may appear transparent, yellow, black, or red.