Hash may refer to:
- Substances
- Hashish, a psychoactive drug
- Hash (food), a coarse mixture of ingredients
- Organizations
- Hash House Harriers, a running club
- Hash mark
- Hash marks, a marking on hockey rinks and gridiron football fields
- Hatch mark, a form of mathematical notation
- Service stripe, a military decoration
- Tally mark, a counting notation
- In linguistics
- Hash symbol or hash mark, the glyph #
- Hashtag, a form of metadata often used on social networking websites
- In computing
- Hash function, a derivation of data, notably seen in cryptographic hash functions
- Hash table, a data structure
- hash (Unix), an operating system command
- Fragment identifier, in computer hypertext, a string of characters that refers to a subordinate resource
- Geohash, a spatial data structure which subdivides space into buckets of grid shape
- Hash chain, a method of producing many one-time keys from a single key or password
- In media
- Hash (film), a 2005 film