| Honorific Prefix: | The Right Honourable |
| The Earl of Leven and Melville | |
| Honorific Suffix: | DL JP |
| Office: | Scottish representative peer |
| Term Start: | 28 July 1865 |
| Term End: | 16 September 1876 |
| Predecessor: | The Lord Rollo |
| Successor: | The Earl of Lauderdale |
| Birth Name: | John Thornton Leslie-Melville |
| Birth Date: | 18 December 1786 |
| Party: | Conservative |
| Parents: | Alexander Leslie-Melville, 7th Earl of Leven Jane Thornton |
| Spouse: | |
| Relations: | David Leslie-Melville, 8th Earl of Leven (brother) John Thornton (grandfather) Samuel Thornton (uncle) Henry Thornton (uncle) |
John Thornton Leslie-Melville, 9th Earl of Leven, 8th Earl of Melville DL JP (18 December 1786 – 16 September 1876) was a Scottish peer and soldier.
John Thornton was born on 18 December 1786. He was the son of Alexander Leslie-Melville, 7th Earl of Leven and the former Jane Thornton (1757–1818). His siblings included the Hon. William Leslie-Melville, the Hon. and Rev. Robert Leslie-Melville, the Hon. Alexander Leslie-Melville of Branston Hall, Lady Lucy Leslie-Melville (wife of Henry Smith), Lady Jane Leslie-Melville (wife of Francis Pym), and Lady Marianne Leslie-Melville (wife of Abel Smith).
His paternal grandfather was David Melville, 6th Earl of Leven (who also sat in the House of Lords as a Scottish representative peer), and his maternal grandfather was merchant and philanthropist John Thornton.
As his brother, David Leslie-Melville, 8th Earl of Leven, died without surviving male issue, he succeeded as the 11th Earl of Leven in 1860.[1] The Earldom of Melville has been held by the Earls of Leven since 20 May 1707.[2]
He was Deputy Paymaster to the Forces in the Peninsula in 1809; he was a founding partner in the banking partnership Williams, Deacon, Labouchere, Thornton & Co; he was a Representative Peer for Scotland (Conservative) from 1865 to 1876.[1]
On 15 September 1812, he married his cousin, Harriet Thornton, daughter of Samuel Thornton, MP and Elizabeth (née Milnes) Thornton (a daughter of Robert Milnes). Together, they were the parents of:[1]
After the death of his first wife, he married another cousin, Sophia Thornton (1806–1887) on 23 April 1834. Sophia, who was also a cousin of his first wife Harriet, was the fourth daughter of reformer Henry Thornton (brother of Samuel Thornton, above). Together, they were the parents of the following children:[1]
Lord Leven died on 16 September 1876 and was succeeded in the earldoms by his eldest surviving son, Alexander. He is buried with his second wife Sophia on the south side of the southern roundel in Brompton Cemetery in London.[4]