Born at Hampton, Edmonstone was Member of Parliament for Stirlingshire from 1874 to 1880, and an Aide-de-Camp to Queen Victoria. He was an admiral in the Royal Navy, and was appointed a Companion of the Order of the Bath (CB).
Sir William Edmonstone died at home, 11 Ainslie Place on the Moray Estate in Edinburgh on 18 February 1888, and was succeeded in the baronetcy by his only surviving son, Archibald Edmonstone. Lady Edmonstone died at Cramond House north-west of Edinburgh, on 11 August 1902.
Edmonstone married at Zakynthos, Greece, on 13 July 1841, Mary Elizabeth Parsons (Newburn, Fife, 21 June 1823 – Cramond House, Midlothian, 11 August 1902), daughter of Lieutenant-Colonel Parsons, CMG, who was British Resident on the island of Zante, at a time when the Ionian Islands were a British Protectorate. Mary Elizabeth and Sir William in all had eleven children, nine of whom survived into adulthood:
- Mary Emma Frances (1842–1847), died when she was five
- Archibald Edmonstone, died in infancy; their second son (see below) bore the same name.
- Jessie Edmondstone (d. 10 June 1937)
- Louisa Ann Edmonstone (d. 3 July 1921)
- Charlotte Henrietta Edmonstone (d. 21 October 1931), married in 1866 John Francis Kitson.
- Frances Euphemia Edmonstone (d. 14 February 1921)
- Sophia Edmonstone (d. 19 February 1924)
- Susanna Emily Edmonstone (d. 9 May 1886)
- Mary Clementina Edmondstone (1857 – 2 December 1922) married Andrew Graham Murray, Viscount Dunedin
- Sir Archibald Edmonstone of Duntreath, 5th Bt. (30 May 1867 – 1 April 1954)
- Alice Frederica Edmonstone (29 April 1868 or 14 October 1869 – 11 September 1947), a British socialite and one of the many mistresses of Edward VII of the United Kingdom; her great granddaughter Camilla, Duchess of Cornwall (née Shand, born 17 July 1947) is the second wife of Charles, Prince of Wales.
- O'Byrne, William Richard (1849). " Edmonstone, William". A Naval Biographical Dictionary. John Murray. Wikisource.
- Edinburgh Post Office Directory 1888
- "Deaths". The Times (36845). London. 13 August 1902. p. 1.
- Lodge, Edmund (1877). The Peerage and Baronetage of the British Empire as at Present Existing. Hurst and Blackett, Publishers. p. 742. Retrieved 17 March 2018.
- Portrait in National Portrait Gallery catalogue
- Hansard 1803–2005: contributions in Parliament by William Edmonstone
|Parliament of the United Kingdom|
| Member of Parliament for Stirlingshire
Joseph Cheney Bolton
|Baronetage of Great Britain|