| Honorific-Prefix: | The Most Honourable |
| The Marquess of Bath | |
| Order1: | Under-Secretary of State for India |
| Term Start1: | 20 January 1905 |
| Term End1: | 4 December 1905 |
| Monarch1: | Edward VII |
| Primeminister1: | Arthur Balfour |
| Predecessor1: | Earl Percy |
| Successor1: | John Ellis |
| Order2: | Master of the Horse |
| Term Start2: | 20 November 1922 |
| Term End2: | 22 January 1924 |
| Monarch2: | George V |
| Primeminister2: | Bonar Law Stanley Baldwin |
| Predecessor2: | The Earl of Chesterfield |
| Successor2: | The Earl of Granard |
| Birth Place: | The Stable Yard, St James's, London |
| Nationality: | British |
| Party: | Conservative |
| Alma Mater: | Balliol College, Oxford |
| Children: | 5, including Henry |
Thomas Henry Thynne, 5th Marquess of Bath (15 July 1862 – 9 June 1946), styled Viscount Weymouth until 1896, was a British landowner and Conservative politician. He held ministerial office as Under-Secretary of State for India in 1905 and Master of the Horse between 1922 and 1924. He was also involved in local politics and served as Chairman of Wiltshire County Council between 1906 and his death in 1946.
Known from birth by the courtesy title of Viscount Weymouth, he was born at the Stable Yard, St James's, Westminster, the eldest son of John Thynne, 4th Marquess of Bath, by the Honourable Frances Isabella Catherine Vesey, a daughter of Thomas Vesey, 3rd Viscount de Vesci. He was educated at Eton and Balliol College, Oxford,[1] where he graduated BA in 1886, in 1888 promoted by seniority to MA.[2]
Lord Weymouth sat as Member of Parliament for Frome between 1886 and 1892 and from 1895 to 1896, when he succeeded his father in the marquessate and entered the House of Lords.[3] He served under Arthur Balfour as Under-Secretary of State for India between January and December 1905. He was appointed Lord Lieutenant of Somerset in 1904 and Chairman of Wiltshire County Council in 1906, and held both posts simultaneously until his death in 1946.[4]
Lord Bath was made a Knight Companion of the Garter in 1917. He returned to the government in 1922, when Bonar Law appointed him Master of the Horse. He was sworn of the Privy Council at the same time. He continued in this office until the Conservative government fell in January 1924, the last year under the premiership of Stanley Baldwin.
Lord Bath was also a Lieutenant-Colonel in the Royal Wiltshire Yeomanry and an Honorary Colonel of that regiment and of the 4th Battalion of the Somerset Light Infantry. In 1937 he was appointed Pro-Chancellor of Bristol University.[5]
On 19 April 1890, Lord Bath married Violet Caroline Mordaunt (28 February 1869–29 May 1928), daughter of Harriet, Lady Mordaunt. At the time of Violet's birth her mother had been the wife of Sir Charles Mordaunt, 10th Baronet, but she was said to be the illegitimate daughter of Viscount Cole, who was later co-respondent in a divorce action.[6] They had five children:
The Marchioness of Bath died in May 1928, aged 59. Lord Bath paid for the construction of a village hall at Horningsham, near the family seat at Longleat, as a memorial to her.[10] He remained a widower until his death in June 1946, aged 83. He was succeeded by his second and only surviving son, Henry.[5]