Steven Bell was born in Walthamstow, London, on 26 February 1951, and raised in Slough. He enjoyed cartoons from a young age, and his influences included Daily Mail cartoonist Leslie Illingworth, Wally Fawkes, Leo Baxendale and David Low, his favourite being Ronald Searle. In 1968 he and his family moved to North Yorkshire.
He studied at Teeside College of Art, but became disillusioned with their narrow interpretation of the field, and left to study filmmaking at the University of Leeds, where he drew posters for the Film Society, graduating in 1974. He then trained as a teacher at St. Luke's College, Exeter, and took a job teaching art at a secondary school in Birmingham.
At the same time he was contributing to the local alternative paper Birmingham Broadside, where he drew the comic strip "Maxwell the Mutant: Marauding the Midlands", the story of a man who gained the power of shape-changing after drinking a contaminated pint of mild. His arch-enemy was Neville Worthyboss, a caricature of the then Tory leader of Birmingham City Council, Neville Bosworth. In 1977 he resigned his teaching job to go full-time as a freelance cartoonist.
His first regular gig was "Dick Doobie the Back to Front Man" in Whoopee! in 1978. He drew "Gremlins" for Jackpot from 1979 to 1982, and also drew for Cheeky Weekly. He began drawing "Maggie's Farm, a political fantasy strip satirising Margaret Thatcher's government, for London listings magazine Time Out in 1979 (it later moved to City Limits magazine and ended in 1987), and from 1980 he drew "Lord God Almighty" for a left wing magazine, The Leveller. Also in 1980, he created a cartoon interpretation of the song "Ivan Meets GI Joe" on the inner sleeve of The Clash's triple album Sandinista!.
Since 1981 he has drawn the daily strip If..., a wide-ranging, and often strem-of-consciousness, left-wing political satire featuring caricatures of politicians and various symbolic characters, for The Guardian, and since 1994 he has also drawn regular editorial cartoons for the same paper, taking over from Les Gibbard and later alternating with Martin Rowson and others. He famously caricatured John Major with his underpants outside his suit, as a "crap superman", and George W. Bush as a chimpanzee. He drew Margaret Thatcher and Tony Blair with the same "mad left eye", and eventually was able to caricature Blair as nothing but a pair of lop-sided eyes, a pair of sticking-out ears and a broad toothy grin, which he could work into all sorts of images.
He has also contributed to Private Eye, New Society, Social Work Today, NME, The Journalist, and the New Statesman. Many collections of his cartoons have been published, and he has illustrated books by a variety of authors. He collaborated with Bob Godfrey on a number of animated short films, including a series for Channel 4 in 1999 to mark the 20th anniversary of Margaret Thatcher's prime ministership, called Margaret Thatcher: Where Am I Now?.
He is married with four grown-up children, and lives in Brighton.