William Murray, 1st Earl of Mansfield, Scottish lawyer, judge, and politician, Chancellor of the Exchequer (d. 1793)
William Murray, 1st Earl of Mansfield, PC, SL (2 March 1705 – 20 March 1793) was a British barrister, politician and judge noted for his reform of English law. Born to Scottish nobility, he was educated in Perth, Scotland, before moving to London at the age of 13 to take up a place at Westminster School. He was accepted into Christ Church, Oxford, in May 1723, and graduated four years later. Returning to London from Oxford, he was called to the Bar by Lincoln's Inn on 23 November 1730, and quickly gained a reputation as an excellent barrister.

He became involved in politics in 1742, beginning with his election as a Member of Parliament for Boroughbridge, now in North Yorkshire, and appointment as Solicitor General. In the absence of a strong Attorney General, he became the main spokesman for the government in the House of Commons, and was noted for his "great powers of eloquence" and described as "beyond comparison the best speaker" in the House of Commons. With the promotion of Sir Dudley Ryder to Lord Chief Justice in 1754, he became Attorney General, and when Ryder unexpectedly died several months later, he took his place as Chief Justice.

As the most powerful British jurist of the century, Mansfield's decisions reflected the Age of Enlightenment and moved the country onto the path to abolishing slavery. He advanced commercial law in ways that helped establish the nation as world leader in industry, finance and trade. He modernised both English law and the English courts system; he rationalized the system for submitting motions and reformed the way judgments were delivered to reduce expense for the parties. For his work in Carter v Boehm and Pillans v Van Mierop, he has been called the founder of English commercial law. He is perhaps now best known for his judgment in Somersett's Case (1772), where he held that slavery had no basis in common law and had never been established by positive law (legislation) in England, and therefore was not binding in law; this judgement did not, however, outlaw the slave trade. However, historians note that Mansfield's ruling in the Somersett case only made it illegal to transport a slave out of England against his will, and did not comment on the institution of slavery itself.