Psion PLC was a designer and manufacturer of mobile handheld computers for commercial and industrial uses. The company was headquartered in London, England, with major operations in Mississauga, Ontario, Canada, and other company offices in Europe, the United States, Asia, Latin America, and the Middle East. It was a public company listed on the London Stock Exchange and was once a constituent of the FTSE 100 Index.

Psion Organiser was the brand name of a range of pocket computers developed by the British company Psion in the 1980s. The Organiser I and Organiser II had a characteristic hard plastic sliding cover protecting a 6×6 keypad instead of a computer keyboard, with letters arranged alphabetically.