McDowell was born in Horsforth, Yorkshire, England, UK. He received acting training at the London Academy of Music and Dramatic Art. His first film role was rebellious student Mick Travis in If... in 1968. This role caught the attention of Stanley Kubrick, who cast him as Alex, a young sociopath in a dystopian future Britain, in A Clockwork Orange. In 1994 he appeared in Star Trek Generations as the mad scientist Dr. Tolian Soran, a role which won him the ire of some Star Trek fans, who saw him as the "man who killed Kirk." One of his other notable voice acting roles is that of President John Henry Eden, the primary antagonist in Bethesda's post-apocalyptic role-playing game Fallout 3.