The ARM is a 32-bit reduced instruction set computer (RISC) instruction set architecture (ISA) developed by ARM Limited. It was known as the Advanced RISC Machine, and before that as the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in terms of numbers produced. They were originally conceived as a processor for desktop personal computers by Acorn Computers, a market now dominated by the x86 family used by IBM PC compatible computers. But the relative simplicity of ARM processors made them suitable for low power applications. This has made them dominant in the mobile and embedded electronics market as relatively low cost and small microprocessors and microcontrollers.

As of 2007, about 98 percent of the more than a billion mobile phones sold each year use at least one ARM processor. As of 2009, ARM processors account for approximately 90% of all embedded 32-bit RISC processors. ARM processors are used extensively in consumer electronics, including PDAs, mobile phones, iPods and other digital media and music players, hand-held game consoles, calculators and computer peripherals such as hard drives and routers.

The ARM architecture is licensable. Companies that are currently or formerly ARM licensees include Alcatel, Atmel, Broadcom, Cirrus Logic, Digital Equipment Corporation, Freescale, Intel (through DEC), LG, Marvell Technology Group, NEC, NVIDIA, NXP (previously Philips), Oki, Qualcomm, Samsung, Sharp, ST Microelectronics, Symbios Logic, Texas Instruments, VLSI Technology, Yamaha and ZiiLABS.

ARM processors are developed by ARM and by ARM licensees. Prominent examples of ARM Limited ARM processor families include the ARM7, ARM9, ARM11 and Cortex. Examples of ARM processors developed by major licensees include the DEC StrongARM, Freescale's i.MX, Marvell (formerly Intel) XScale, NVIDIA's Tegra, ST-Ericsson Nomadik, and Qualcomm's Snapdragon.