Thomas Thynne, 5th Marquess of Bath

Thomas Henry Thynne, 5th Marquess of Bath KG CB PC JP (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 by the courtesy title Viscount Weymouth from birth, he was born at The Stable Yard, St James's, London, the eldest son of John Thynne, 4th Marquess of Bath, by the Honourable Frances Isabella Catherine Vesey, daughter of Thomas Vesey, 3rd Viscount de Vesci. He was educated at Eton and Balliol College, Oxford, graduating in 1886 with a Bachelor of Arts (BA) and in 1888 with a Master of Arts (MA) degree.

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. 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.

Lord Bath was made a Knight of the Garter in 1917. He returned to the government in 1922, when Andrew 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.

On 19 April 1890, Lord Bath married Violet Caroline Mordaunt, daughter of Harriet, Lady Mordaunt, who at the time of her birth had been the wife of Sir Charles Mordaunt, 10th Baronet, but the child was said to be the illegitimate daughter of Viscount Cole, who was later co-respondent in a divorce action. They had five children:

• Lady Alice Kathleen Violet Thynne (1891–1977), married Lt-Col Oliver Stanley, son of Edward Stanley, 4th Baron Sheffield and had issue.
• Lady Emma Margery Thynne (1893–1980), married 1921 (div 1942) William Compton, 6th Marquess of Northampton; no issue.
• 2nd Lt. John Alexander Thynne, Viscount Weymouth (1895–1916), killed in the First World War, unmarried.
• Lady Mary Beatrice Thynne (1903–1974), married firstly, Charles Wilson, 3rd Baron Nunburnholme and had issue. She married secondly, Ulick Alexander. She was a bridesmaid at the wedding of Prince Albert, Duke of York, and Lady Elizabeth Bowes-Lyon on 3 May 1923.
• Henry Frederick Thynne, 6th Marquess of Bath (1905–1992)

The Marchioness of Bath died in May 1928, aged 59. Lord Bath remained a widower until his death in June 1946, aged 83. He was succeeded by his second and only surviving son, Henry.