Sir William Blackstone (10 July 1723 – 14 February 1780) was an English jurist, justice, and Tory politician most noted for his Commentaries on the Laws of England, which became the best-known description of the doctrines of the English common law. Born into a middle-class family in London, Blackstone was educated at Charterhouse School before matriculating at Pembroke College, Oxford, in 1738. After switching to and completing a Bachelor of Civil Law degree, he was made a fellow of All Souls College, Oxford, on 2 November 1743, admitted to Middle Temple, and called to the Bar there in 1746. Following a slow start to his career as a barrister, Blackstone was involved heavily in university administration, becoming accountant, treasurer, and bursar on 28 November 1746, and Senior Bursar in 1750. Blackstone is considered responsible for completing the Codrington Library and the Warton Building, and for simplifying the complex accounting system used by the college. On 3 July, 1753, he formally gave up his practice as a barrister, and embarked on a series of lectures on English law, the first of their kind. These talks were massively successful, earning him £453 (£94,000 in 2025 terms); they led to the publication of An Analysis of the Laws of England in 1756, which sold out repeatedly. It was used to preface his later works.

On 20 October, 1759, Blackstone was confirmed as the first Vinerian Professor of English Law, immediately embarking on another series of lectures and publishing a similarly successful second treatise, A Discourse on the Study of the Law. With his growing fame, he successfully returned to the bar and maintained a good practice, also securing election as Tory Member of Parliament for the rotten borough of Hindon on 30 March 1761. In November 1765 he published the first of four volumes of Commentaries on the Laws of England, considered his magnum opus; the completed work earned Blackstone £14,000 (£2,459,000 in 2023 terms). After repeated failures, he gained appointment to the judiciary as a justice of the Court of King's Bench on 16 February 1770, leaving to replace Edward Clive as a justice of the Common Pleas on 25 June. He remained in this position until his death, on 14 February 1780.

Blackstone's four-volume Commentaries were designed to provide a complete overview of English law and were republished in 1770, 1773, 1774, 1775, 1778, and in a posthumous edition in 1783. Reprints of the first edition, intended for practical use rather than antiquary interest, were published until the 1870s in England and Wales, and a working version by Henry John Stephen, first published in 1841, was reprinted until after the Second World War. Legal education in England had stalled; Blackstone's work gave the law "at least a veneer of scholarly respectability". William Searle Holdsworth, one of Blackstone's successors as Vinerian Professor, argued that "If the Commentaries had not been written when they were written, I think it very doubtful that the United States, and other English speaking countries would have so universally adopted the common law." In the United States, the Commentaries influenced Alexander Hamilton, John Marshall, James Wilson, John Jay, John Adams, James Kent and Abraham Lincoln, and remain frequently cited in Supreme Court decisions.

Blackstone was the fourth and posthumous son of Charles Blackstone, a silk mercer from Cheapside, the son of a wealthy apothecary. He became firm friends with Thomas Bigg, a surgeon and the son of Lovelace Bigg, a gentleman from Wiltshire. After Bigg's sister Mary came to London, Charles eventually persuaded her to marry him in 1718. This was not seen as a good match for her, but the couple lived happily and had four sons, three of whom lived into adulthood. Charles (born August 1719) and Henry (May 1722), both became fellows of New College, Oxford, and took holy orders. Their last son, William, was born on 10 July 1723, five months after Charles' death in February.

Although Charles and Mary Blackstone were members of the middle class rather than landed gentry, they were particularly prosperous. Tax records show Charles Blackstone to have been the second most prosperous man in the parish in 1722, and death registers show that the family had several servants. This, along with Thomas Bigg's assistance to the family following Charles' death, helps explain the educational upbringing of the children. William Blackstone was sent to Charterhouse School in 1730 having been nominated by Charles Wither, a relative of Mary Blackstone. William did well there, and became head of the school by age 15. However, after Charles' death the family fortunes declined, and after Mary died (5 January 1736) the family's resources largely went to meet unpaid bills. William was able to remain at Charterhouse as a "poor scholar", having been named to that position in June 1735 after being nominated by Sir Robert Walpole.

Blackstone revelled in Charterhouse's academic curriculum, particularly the Latin poetry of Ovid and Virgil. He began to attract note as a poet at school, writing a 30-line set of rhyming couplets to celebrate the wedding of James Hotchkis, the headmaster. He also won a silver medal for his Latin verses on John Milton, gave the annual Latin oration in 1738, and was noted as having been the favourite student of his masters. On 1 October 1738, taking advantage of a new scholarship available to Charterhouse students, Blackstone matriculated at Pembroke College, Oxford.

There are few surviving records of Blackstone's undergraduate term at Oxford, but the curriculum of Pembroke College had been set out in 1624, and Wilfrid Prest notes that it was probably still followed in 1738, so Blackstone would have studied Greek, science, logic, rhetoric, philosophy, mathematics, geography and poetry. Blackstone was particularly good at Greek, mathematics, and poetry, with his notes on William Shakespeare being included in George Steevens' 1781 edition of Shakespeare's plays. Many of Blackstone's undergraduate texts survive, and they include few legal texts, instead being wide-ranging: politics, current affairs, poetry, geometry, and controversial theological texts. The last element is understandable, given his family's theological interests, but the more surprising element is the sheer number of texts he owned, given his relative poverty as a student.

On 9 July 1740, after only a year and a half as a Bachelor of Arts student, Blackstone was admitted to study for a Bachelor of Civil Law degree, civil law being the only legal area recognised by his university. This degree course was seven years long, the first two "supposedly devoted to a broad course of reading in humane studies", which allowed him to study his own interests. On 20 November 1741 he was admitted to the Middle Temple, the first step on the road to becoming a barrister, but this imposed no obligations and simply allowed a legal career to be an option. At the time there was no proper legal education system, and Blackstone read (in his own time) Coke on Littleton, the works of Henry Finch, and related legal tracts.