Osbourne was born in the Aston area of Birmingham, England. His mother, Lilian (née Unitt; 1916–2001), was a non-observant Catholic who worked days at a factory. His father, John Thomas "Jack" Osbourne (1915–1977), worked night shifts as a toolmaker at the General Electric Company. Osbourne has three older sisters named Jean, Iris, and Gillian, and two younger brothers named Paul and Tony. The family lived in a small two-bedroom home at 14 Lodge Road in Aston. Osbourne has had the nickname "Ozzy" since primary school. Osbourne dealt with dyslexia at school. At the age of 11, he suffered sexual abuse from school bullies. Drawn to the stage, he took part in school plays such as Gilbert and Sullivan's The Mikado and HMS Pinafore. As a Birmingham native, he has a strong Brummie accent.
Upon hearing their first hit single at age 14, Osbourne became a great fan of the Beatles. He credits the band's 1963 song "She Loves You" for inspiring him to become a musician. He said in the 2011 documentary God Bless Ozzy Osbourne, "I knew I was going to be a rock star the rest of my life." Osbourne left school at 15 and was employed as a construction site labourer, trainee plumber, apprentice toolmaker, car factory horn-tuner, and abattoir worker. He attempted to commit burglary, stealing a television (which fell on him during his getaway and had to be abandoned), a handful of baby clothes (originally thought to be adult clothes as it was too dark to see when he committed the burglary, and which were stolen to sell to people at a pub), and some T-shirts. He spent six weeks in Winson Green Prison when he was unable to pay a fine after being found guilty of robbing a clothes shop; to teach his son a lesson, his father refused to pay the fine.