Gary Anthony James Webb was born on 8 March 1958 in Hammersmith, West London, the son of a British Airways bus driver based at Heathrow Airport. He was educated at Town Farm Junior School in Stanwell, Surrey, Ashford County Grammar School, then Slough Grammar School in Berkshire, followed by Brooklands Technical College in Surrey. He joined the Air Training Corps as a teenager. He then briefly held various jobs including forklift truck driver, air conditioning ventilator fitter, and accounts clerk.
When Numan was 15 years old, his father bought him a Gibson Les Paul, which he regards as his most treasured possession. He played in various bands, including Mean Street and the Lasers, before forming Tubeway Army with his uncle, Jess Lidyard, and Paul Gardiner. His initial pseudonym was "Valerian", probably in reference to the hero in French science fiction comic series Valérian and Laureline. He later picked the surname "Numan" from an advert in the Yellow pages for a plumber whose surname was "Neumann".