Walter Francis Montagu Douglas Scott, 5th Duke of Buccleuch, 7th Duke of Queensberry, KG, PC, FRS, FRSE (25 November 1806 – 16 April 1884), styled Lord Eskdail between 1808 and 1812 and Earl of Dalkeith between 1812 and 1819, was a prominent Scottish nobleman, landowner and politician. He was Lord Keeper of the Privy Seal from 1842 to 1846 and Lord President of the Council. 
 Buccleuch was born at the Palace of Dalkeith, Midlothian, Scotland, the fifth child of seven, and second son of Charles Montagu-Scott, 4th Duke of Buccleuch, and Hon. Harriet Katherine Townshend, daughter of Thomas Townshend, 1st Viscount Sydney and Elizabeth Powys. When his older brother, George Henry, died at the age of 10 from measles, Walter became heir apparent to the Dukedoms of Buccleuch and Queensberry. He was only thirteen when he succeeded his father to the Dukedoms of Buccleuch and Queensberry in 1819. He also inherited 460,000 acres, including 254,000 acres in Dumfries, 104,000 acres in Roxburgh and 60,000 acres in Selkirk. He was educated at Eton and St John's College, Cambridge (M.A., 1827). In June 1833 he was elected a Fellow of the Royal Society. In 1841, he played in two first-class cricket matches for Marylebone Cricket Club. He was made an honorary member of the Institution of Civil Engineers on the  28th of June, 1812 in recognition of his involvement in great works of engineering in Scotland, such as Granton Harbour. Buccleuch set out his ideas of the duties of a great landowner in a speech given at  Branxholme Fete in 1839: 
 What has been entrusted to me has not been given that it might be wasted in idle or frivolous amusements; nor would I be justified in wasting the hard earnings of the tillers of the soil by carrying them away and spending them in foreign countries, but I wish to see them employed as the means of producing good to them and to the country at large. Buccleuch, Lord of the Liberty and Manors of Furness, and owner of extensive iron-mines in the area was, in conjunction with William Cavendish, 7th Duke of Devonshire, a main sponsor of the Furness Railway. He bought up a great eal of land in the area, and rebuilt Lindal-in-Furness as a model village.
 A great Scottish land magnate, Buccleuch was a Conservative in politics, and was appointed a Knight of the Garter in 1835 and a Privy Counsellor in 1842. He served as Lord Privy Seal from 1842 to 1846 and as Lord President of the Council from January to July 1846 in Peel's government, when he reluctantly supported Peel's decision to repeal the Corn Laws. After Peel's fall, the Duke's political career largely came to an end. In 1878 he became Chancellor of the University of Glasgow, a post he held until his death in 1884.
 On 6 January 1842 he was appointed Colonel of the Edinburgh Militia (a regiment that his grandfather the 3rd Duke had raised in 1798). He was appointed an Aide-de-Camp to Queen Victoria for the militia on 19 March 1857. On resigning from the command on 20 May 1879 he was appointed the first Honorary Colonel of the Queen's Edinburgh Light Infantry Militia, as the regiment had by then become.
 He joined the Canterbury Association on 20 May 1848. It was planned to build a town called Buccleuch in his honour near Alford Forest, but this did not eventuate.
 Buccleuch married Lady Charlotte Anne Thynne, daughter of Thomas Thynne, 2nd Marquess of Bath and Hon. Isabella Elizabeth Byng, daughter of the 4th Viscount Torrington, on 13 August 1829 at St George's church, Hanover Square, London. The couple had four sons and three daughters:
 King George IV spent some days in 1822 as the Duke's guest at Dalkeith Palace, the first visit of a reigning Hanoverian monarch to Scotland. Twenty years later, Queen Victoria also honoured him with a visit. The family continued to hold a high profile in royal circles, being invited to the Coronations of William IV and Victoria, with the Duke acting as Gold Stick.
 The story goes that in 1879 the Historical Manuscripts Commission discovered an old black box amongst the Duke of Buccleuch's papers at Dalkeith, which was found to contain a contract proving Charles II had married Lucy Walter. In fact, the document meant the Duke was the rightful King of the United Kingdom, being the eldest agnatic descendant of James Scott, 1st Duke of Monmouth. When he was shown the deed, he threw it on the fire, remarking, "that might cause a lot of trouble".
 Buccleuch died at Bowhill House near Bowhill, Selkirkshire, in April 1884, aged 77, and was succeeded by his eldest son, William. He was buried in the family crypt of the Buccleuch Memorial Chapel in St. Mary's Episcopal Church, Dalkeith, Midlothian. The church is located on Dalkeith's High Street, at the entrance to Dalkeith Country Park.