The term arm or ARM may refer to the following:
- an area of the upper human body generally thought of as being from the shoulder to the fingers of the hand
- a geographical term for a small or narrow branch, extension or inlet flowing out of a larger body of water
- a family of instruction set architechtures for computers by ARM Holdings on based on RISC (reduced instruction set computing) architechture
- Application Response Measurement, an open standard for monitoring and diagnosing performance bottlenecks in applications
- Abstract Rewriting Machine, a type of virtual machine for term rewriting
- Asteroid Redirect Mission (ARM, also Asteriod Retrieval and Utilization, ARU), a future space mission proposed by NASA
- Atmospheric Radation Measurement, a program and set of scientific facilities by the US Department of Energy devoted to the study of global climate change
- Anti-radiation missile, a type of missile designed to detect and target radio emission sources, such as radar
- Anonymizing relay monitor, a command-line interface status monitor written in Python for the anonimity software (and network), Tor
- ARM, a science-fiction novella written by American author, Larry Niven
- Armageddon (or Arm), a low fantasy MUD (Multi-User Dungeon), a type of text-based computer role-playing game
- ARM Holdings plc, a British semiconductor and software design company known for their RISC-based ARM architechture for computer processors
- African Resistance Movement, a militant anti-apartheid movement active in South Africa in the 1960's
- Animal Rights Militia, a banner used by alleged animal rights activists in Europe and North America to engage in direct action that may be considered borderline to outright illegal
- Army of the Republic of Macedonia, a name for the unified armed forces of the Republic of Macedonia
- Macau Amateur Radio Society (traditional Chinese: ?????????, Portugese: Associação dos Radioamadores de Macau), a non-profit organization for amateur radio enthusiasts in the Special Administrative Region of Macau
- Amateur Radio Society of Moldova (Romanian: Asocia?ia Radioamatorilor din Moldova), a non-profit organization for radio enthusiasts in the country of Moldova
- Association of Radical Midwives, an organisation in the UK for people concerned in matters of childbirth and maternity services
- Association of Railway Museums, one of the constituent organizations of the Association of Tourist Railways and Railway Museums, an association dedicated to promoting and preserving North American Railway culture
- Association of Recovering Motorcyclists, an independent motorcycle association with chapters in various countries
- Australian Republican Movement, a non-partisan lobby group advocating for Australia to change from a constitutional monarchy into a republican form of government
- Armenia, with the ISO 3166-1 alpha-3 code ARM
- the names of rivers in Tasmania in Australia and Saskatchewan in Canada, respectivel
- Armenian language, with the ISO 639-2 code of ARM
- Adjustable-rate mortgage (also variable-rate mortgage, tracker mortgage), a type of mortgage loan with a variable interest rate
- Anorectal malformation (or imperforate anus), a birth defect wherein the infant's rectum is malformed