Stephen William Hawking (8 January 1942 – 14 March 2018) was an English theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge. Between 1979 and 2009, he was the Lucasian Professor of Mathematics at Cambridge, widely viewed as one of the most prestigious academic posts in the world.

Hawking was born in Oxford into a family of physicians. In October 1959, at the age of 17, he began his university education at University College, Oxford, where he received a first-class BA degree in physics. In October 1962, he began his graduate work at Trinity Hall, Cambridge, where, in March 1966, he obtained his PhD in applied mathematics and theoretical physics, specialising in general relativity and cosmology. In 1963, at age 21, Hawking was diagnosed with an early-onset slow-progressing form of motor neurone disease that gradually, over decades, paralysed him. After the loss of his speech, he communicated through a speech-generating device, initially through use of a handheld switch, and eventually by using a single cheek muscle.

Hawking's scientific works included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity, and the theoretical prediction that black holes emit radiation, often called Hawking radiation. Initially, Hawking radiation was controversial. By the late 1970s, and following the publication of further research, the discovery was widely accepted as a major breakthrough in theoretical physics. Hawking was the first to set out a theory of cosmology explained by a union of the general theory of relativity and quantum mechanics. Hawking was a vigorous supporter of the many-worlds interpretation of quantum mechanics. He also introduced the notion of a micro black hole.

Hawking achieved commercial success with several works of popular science in which he discussed his theories and cosmology in general. His book A Brief History of Time appeared on the Sunday Times bestseller list for a record-breaking 237 weeks. Hawking was a Fellow of the Royal Society, a lifetime member of the Pontifical Academy of Sciences, and a recipient of the Presidential Medal of Freedom, the highest civilian award in the United States. In 2002, Hawking was ranked number 25 in the BBC's poll of the 100 Greatest Britons. He died in 2018 at the age of 76, having lived more than 50 years following his diagnosis of motor neurone disease.

Stephen William Hawking was born on 8 January 1942 in Oxford to Frank and Isobel Eileen Hawking (née Walker). Hawking's mother was born into a family of doctors in Glasgow, Scotland. His wealthy paternal great-grandfather, from Yorkshire, over-extended himself buying farm land and then went bankrupt in the great agricultural depression during the early 20th century. His paternal great-grandmother saved the family from financial ruin by opening a school in their home. Despite their families' financial constraints, both parents attended the University of Oxford, where Frank read medicine and Isobel read Philosophy, Politics and Economics. Isobel worked as a secretary for a medical research institute, and Frank was a medical researcher specialising in tropical diseases. Hawking said of his father, "I modelled myself on him. Because he was a scientific researcher, I felt that scientific research was the natural thing to do when one grew up. The only difference was that I was not attracted to medicine or biology because they seemed too inexact and descriptive. I wanted something more fundamental, and I found it in physics."

In 1950, when Hawking's father became head of the division of parasitology at the National Institute for Medical Research, the family moved to St Albans, Hertfordshire. In St Albans, the family was considered highly intelligent and somewhat eccentric; meals were often spent with each person silently reading a book. They lived a frugal existence in a large, cluttered, and poorly maintained house and travelled in a converted London taxicab. During one of Hawking's father's frequent absences working in Africa, the rest of the family spent four months in Mallorca visiting his mother's friend Beryl and her husband, the poet Robert Graves.

Hawking began his schooling at the Byron House School in Highgate, London. He later blamed its "progressive methods" for his failure to learn to read while at the school. In St Albans, the eight-year-old Hawking attended St Albans High School for Girls for a few months. At that time, younger boys could attend one of the houses.

Hawking attended two private (i.e. fee-paying) schools, first Radlett School and from September 1952, St Albans School, Hertfordshire, after passing the eleven-plus a year early. The family placed a high value on education. Hawking's father wanted his son to attend Westminster School, but the 13-year-old Hawking was ill on the day of the scholarship examination. His family could not afford the school fees without the financial aid of a scholarship, so Hawking remained at St Albans. A positive consequence was that Hawking remained close to a group of friends with whom he enjoyed board games, the manufacture of fireworks, model aeroplanes and boats, and long discussions about Christianity and extrasensory perception. From 1958 on, with the help of the mathematics teacher Dikran Tahta, they built a computer from clock parts, an old telephone switchboard and other recycled components. In 1959, he built a record player from spare parts: "My father would have regarded it as recklessly self-indulgent, to buy a record player, but I persuaded him that I could assemble one from parts that I could buy cheap. That appealed to him as a Yorkshireman."