William Thomas Horner Fox-Strangways, 4th Earl of Ilchester FRS (7 May 1795 – 10 January 1865), styled The Honourable William Fox-Strangways until 1858, was a British diplomat, Whig politician and art collector.^[1] He served as Under-Secretary of State for Foreign Affairs under Lord Melbourne from 1835 to 1840 and was Envoy Extraordinary and Minister Plenipotentiary to the German Confederation from 1840 to 1849.

Fox-Strangways was the son of Henry Thomas Fox-Strangways, 2nd Earl of Ilchester, and his second wife Maria Digby, daughter of William Digby. Henry Fox-Strangways, 3rd Earl of Ilchester, was his elder half-brother and John Fox-Strangways his younger brother. He was educated at Christ Church, Oxford, taking a BA in 1816 and an MA in 1820.

Fox-Strangways served as an attaché at the British embassies in St Petersburg, Constantinople, Naples and The Hague, as Secretary of Legation in Florence and Naples and as Secretary of Embassy in Vienna.^[2] In 1835 he was appointed Under-Secretary of State for Foreign Affairs in the Whig administration of Lord Melbourne, a post he held until 1840 (however, he was not a Member of Parliament during this time). The latter year he was appointed Envoy Extraordinary and Minister Plenipotentiary to the German Confederation,^[3] which he remained until 1849. In 1858 he succeeded his half-brother as fourth Earl of Ilchester and entered the House of Lords.

He was elected a Fellow of the Royal Society in March 1821.^[4]

Fox-Strangways was interested in geology and was elected as a Member of the Geological Society in 1815, serving on the Council 1820-1821. When he was attaché at the British Embassy in St Petersburg Fox-Strangways wrote  ‘Geological sketch of the environs of Petersburg’ published in the Transactions of the Geological Society of London in 1821 (read on 16 April 1819), which includes a coloured geological map of the St Petersburg region, distinguishing four rock types, as well as some cross-sections and scenic views along the river banks.^[5] His work was expanded in a paper read to the Geological Society in 1821 published as 'An Outline of the Geology of Russia',^[6] which includes a 'Sketch to serve as a basis for a Geological Map of European Russia Coloured to show the connections of its the Strata with this of the Surrounding Countries'. The map is mineralogical, that is essentially charting lithological types, depicting 24 different types, labelled A to Z. These papers and maps are amongst the earliest published works on the geology of Russia and formed the basis of R. I. Murchison's 'Geology of Russia' (1845). His great nephew Charles Edward Fox-Strangways (1844-1910) was a geologist for the Geological Survey of Great Britain.^[7]

Lord Ilchester married Sophia Penelope Sheffield, daughter of Sir Robert Sheffield, 4th Baronet, in 1857. They had no children. He died in January 1865, aged 69, and was succeeded by his nephew Henry Edward Fox-Strangways. Between 1828 and 1834 Fox-Strangways donated 37 early Italian paintings to Christ Church. There they are still shown at the Christ Church Picture Gallery. "He also left a further 41 paintings to the Ashmolean, including Paolo Ucello's The Hunt.^[8]

The arms of the head of the Fox-Strangways family are blazoned Quarterly of four: 1st & 4th: Sable, two lions passant paly of six argent and gules (Strangways); 2nd & 3rd: Ermine, on a chevron azure three foxes' heads and necks erased or on a canton of the second a fleur-de-lys of the third (Fox).^[9]

• Ilchester Lectures