Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the UK, including the Acorn Electron and the Acorn Archimedes. Acorn's BBC Micro computer dominated the UK educational computer market during the 1980s.

Though the company was acquired and largely dismantled in early 1999, with various activities being dispersed amongst new and established companies, its legacy includes the development of reduced instruction set computing (RISC) personal computers. One of its operating systems, RISC OS, continues to be developed by RISC OS Open. Some activities established by Acorn lived on: technology developed by Arm, created by Acorn as a joint venture with Apple and VLSI in 1990, is dominant in the mobile phone and personal digital assistant (PDA) microprocessor market.

Acorn is sometimes referred to as the "British Apple" and has been compared to Fairchild Semiconductor for being a catalyst for start-ups. In 2010, the company was listed by David Meyer in ZDNet as number nine in a feature of top ten "Dead IT giants". Many British IT professionals gained their early experiences on Acorns, which were often more technically advanced than commercially successful US hardware.