Roald Dahl was born in 1916 at Villa Marie, Fairwater Road, in Llandaff, Cardiff, Wales, to Norwegian parents, Harald Dahl and Sofie Magdalene Dahl (née Hesselberg). Dahl's father had emigrated to the UK from Sarpsborg in Norway, and settled in Cardiff in the 1880s with his first wife, a Frenchwoman named Marie Beaurin-Gresser. They had two children together, Ellen Marguerite and Louis, before her death in 1907. His mother came over and married his father in 1911. Dahl was named after the Norwegian polar explorer Roald Amundsen. His first language was Norwegian, which he spoke at home with his parents and his sisters Astri, Alfhild, and Else. Dahl and his sisters were raised in the Lutheran faith, and were baptised at the Norwegian Church, Cardiff, where their parents worshipped.
Mrs Pratchett's former sweet shop in Llandaff, Cardiff, has a blue plaque
commemorating the mischief played by young Roald Dahl and his friends, who were regular customers.
In 1920, when Dahl was three years old, his seven-year-old sister, Astri, died from appendicitis. Weeks later, his father died of pneumonia at the age of 57. Later that year, his younger sister Asta was born. With the option of returning to Norway to live with relatives, Dahl's mother decided to remain in Wales. Her husband Harald had wanted their children to be educated in English schools, which he considered the world's best.
Dahl first attended the Cathedral School, Llandaff. At the age of eight, he and four of his friends (one named Thwaites) were caned by the headmaster after putting a dead mouse in a jar of gobstoppers at the local sweet shop, which was owned by a "mean and loathsome" old woman called Mrs Pratchett. The five boys named their prank the "Great Mouse Plot of 1924". Gobstoppers were a favourite sweet among British schoolboys between the two World Wars, and Dahl would refer to them in his creation, Everlasting Gobstopper, which was featured in Charlie and the Chocolate Factory.
Dahl transferred to a boarding school in England: St Peter's in Weston-super-Mare. His parents had wanted him to be educated at an English public school and, because of the regular ferry link across the Bristol Channel, this proved to be the nearest. Dahl's time at St Peter's was unpleasant; he was very homesick and wrote to his mother every week but never revealed his unhappiness to her. After her death in 1967, he learned that she had saved every one of his letters, in small bundles held together with green tape. In 2016, to mark the centenary of Dahl's birth, his letters to his mother were abridged and broadcast as BBC Radio 4's Book of the Week. Dahl wrote about his time at St Peter's in his autobiography Boy: Tales of Childhood.
From 1929, when he was 13, Dahl attended Repton School in Derbyshire. Dahl disliked the hazing and described an environment of ritual cruelty and status domination, with younger boys having to act as personal servants for older boys, frequently subject to terrible beatings. His biographer Donald Sturrock described these violent experiences in Dahl's early life. Dahl expresses some of these darker experiences in his writings, which is also marked by his hatred of cruelty and corporal punishment. According to Boy: Tales of Childhood, a friend named Michael was viciously caned by headmaster Geoffrey Fisher. Writing in that same book, Dahl reflected: “All through my school life I was appalled by the fact that masters and senior boys were allowed literally to wound other boys, and sometimes quite severely... I couldn’t get over it. I never have got over it.” The master was later selected as the Archbishop of Canterbury and crowned Queen Elizabeth II in 1953. (According to Dahl's biographer Jeremy Treglown, the caning took place in May 1933, a year after Fisher had left Repton; the headmaster was in fact J. T. Christie, Fisher's successor.) Dahl said the incident caused him to "have doubts about religion and even about God".
He was never seen as a particularly talented writer in his school years, with one of his English teachers writing in his school report "I have never met anybody who so persistently writes words meaning the exact opposite of what is intended." Dahl was exceptionally tall, reaching 6 feet 6 inches (1.98 m) in adult life. He played sports including cricket, and golf, and was made captain of the squash team. As well as having a passion for literature, he developed an interest in photography and often carried a camera with him.
During his years at Repton, the Cadbury chocolate company would occasionally send boxes of new chocolates to the school to be tested by the pupils. Dahl would dream of inventing a new chocolate bar that would win the praise of Mr Cadbury himself; this inspired him in writing his third children's book, Charlie and the Chocolate Factory (1964), and to refer to chocolate in other children's books.
Throughout his childhood and adolescent years, Dahl spent the majority of his summer holidays with his mother's family in Norway. He wrote about many happy memories from those visits in Boy: Tales of Childhood, such as when he replaced the tobacco in his half–sister's fiancé's pipe with goat droppings. He noted only one unhappy memory of his holidays in Norway: at around the age of eight, he had to have his adenoids removed by a doctor. His childhood and first job selling kerosene in Midsomer Norton and surrounding villages in Somerset are subjects in Boy: Tales of Childhood.
After finishing his schooling, in August 1934 Dahl crossed the Atlantic on the RMS Nova Scotia and hiked through Newfoundland with the Public Schools Exploring Society.
In July 1934, Dahl joined the Shell Petroleum Company. Following two years of training in the United Kingdom, he was assigned first to Mombasa, Kenya, then to Dar-es-Salaam, Tanganyika (now Tanzania). Along with the only two other Shell employees in the entire territory, he lived in luxury in the Shell House outside Dar es Salaam, with a cook and personal servants. While out on assignments supplying oil to customers across Tanganyika, he encountered black mambas and lions, among other wildlife.