William Douglas-Hamilton, 12th Duke of Hamilton

William Alexander Louis Stephen Douglas-Hamilton, 12th Duke of Hamilton, 9th Duke of Brandon, 2nd Duke of Châtellerault KT (12 March 1845 in London – 16 May 1895 in Algiers) was a Scottish nobleman.

He was the son of William Hamilton, 11th Duke of Hamilton and Princess Marie of Baden, the adoptive granddaughter of Napoleon Bonaparte. Hamilton was born at Connaught Place, London.

Hamilton was educated at Eton College and Christ Church, Oxford.

A description of Hamilton :"at Christchurch he went in for boxing, as he went in later for horse-racing, yachting and other amusements... He was full bodied, of a rudely ruddy complexion, had a powerful neck, and seemed strong enough to fell an ox with his fist... He had a frankness of speech bordering on rudeness".

On 10 December 1873, he married Lady Mary Montagu, daughter of William Montagu, 7th Duke of Manchester, at Kimbolton Castle and they had one daughter:

• Lady Mary Louise Douglas-Hamilton (1 November 1884 – 21 February 1957), she married James Graham, 6th Duke of Montrose on 14 June 1906. They had four children.

In 1867 he was close to financial ruin when his race horse Cortolvin won the Grand National Steeplechase at Aintree. In addition to substantial prize money he also took some £16,000 from the bookmakers, restoring his fortune.

He died at Algiers in 1895, aged 50 and the title passed to his fourth cousin the thirteenth Duke.