John Andrew Hamilton, 1st Viscount Sumner, GCB, PC (3 February 1859 – 24 May 1934) was a British lawyer and judge. He was appointed a judge of the High Court of Justice (King's Bench Division) in 1909, a Lord Justice of Appeal in 1912 and a Lord of Appeal in Ordinary (Law Lord) in 1913. Created a life peer as Baron Sumner in 1913, he was further honoured when he was granted a hereditary peerage as Viscount Sumner in 1927.

Hamilton was born in Chorlton-upon-Medlock, Lancashire,^[1] the second son of Andrew Hamilton, an iron merchant of Manchester,^[2] and his wife, Frances, daughter of Joseph Sumner.^[3] He was baptised at the Church of St Wilfrid, Northenden.^[4]

Hamilton was educated at Manchester Grammar School and Balliol College, Oxford.^[1] In 1883, he was called to the bar, Inner Temple.^[2] Hamilton was a Fellow of Magdalen College, Oxford, for seven years from 1892 and was nominated an honorary fellow in 1909.^[3] He received an Honorary Doctorate of Laws by the University of Edinburgh in 1913 and by the University of Manchester in 1919.^[5] One year later, Hamilton obtained also an Honorary Doctorate of Civil Law by the University of Oxford.^[5]

Hamilton joined in the Northern Circuit and became a King's Counsel in 1901.^[2] He was elected a standing counsel to the Oxford University in 1906, a post he held for the next three years.^[5] On his appointment as Judge of the High Court of Justice (King's Bench Division) in 1909, he was knighted and invested a bencher.^[2] In 1912 he became a Lord Justice of Appeal and sworn of the Privy Council.^[2] Already in the following year, Hamilton became a Lord of Appeal in Ordinary and created a life peer as Baron Sumner, of Ibstone, in the County of Buckingham.^[6] He was further honoured, when on 31 January 1927, he created a hereditary peerage as Viscount Sumner, of Ibstone, in the County of Buckingham.^[7] Hamilton retired as judge in 1930.^[1]

In 1908, Hamilton was Inspector in the Swansea Education Dispute.^[2] In the House of Lords, he was chairman of the Working Classes Cost of Living, the British Cellulose Enquiry and the British and Foreign Legal Procedure committees.^[2] Hamilton took part at the Treaty of Versailles in 1919 as delegate of the reparations commission, for which he was appointed a Knight Grand Cross of the Order of the Bath (GCB) in the 1920 Birthday Honours.^[2] In the next year, he chaired the Royal Commission on Compensation for Suffering and Damage by Enemy Action.^[5]

In 1892, he married Maude Margaret Todd, the second daughter of Reverend John Wood Todd,^[3] a Baptist minister who with his wife founded what became Tudor Hall School. Hamilton's marriage was childless, and with Hamilton's death, the viscountcy became extinct.^[3]

In 2009, a biography of Lord Sumner was published by Anthony Lentin.^[8]

• Bowman v The Secular Society (1917)
• Elder Dempster & Co v Paterson Zochonis & Co (1924)