System One, System I or System 1 may refer to:
Computing Acorn System 1, 8-bit microcomputer by Acorn Cromemco System One, a microcomputer from the early 1980s by Cromemco IBM Q System One, a 2019 circuit-based commercial quantum computer by IBM Line Drawing System-1, an early graphical computer Sega System 1, the arcade system board System 1, the initial operating system version for the Apple Macintosh Tulip System-1, 16-bit personal computer by Tulip
Other uses System-1 Aira, a synthesizer produced by Roland System One, a range of bus passes offered by Transport for Greater Manchester System 1, the fast, automatic mode of thinking, as described in Daniel Kahneman's book Thinking, Fast and Slow
See also System I (disambiguation) SystmOne, a clinical and administrative software system developed by TPP (The Phoenix Partnership) company. Series 1