William Mansfield, 1st Viscount Sandhurst GCSI, GCIE, GCVO, PC (21 August 1855 – 2 November 1921) was a British Liberal politician and colonial governor.

[1] Mansfield succeeded his father as Baron Sandhurst in 1876, aged 20, and was entitled to a seat in the House of Lords from his 21st birthday a few months later.

[3] Lord Sandhurst did not initially serve in the Liberal administrations headed by Sir Henry Campbell-Bannerman and H. H. Asquith but was sworn of the Privy Council in 1907.

[7] According to the historian David Gilmour, Sandhurst was "regarded by his brother officers in the Coldstream Guards as ‘incurably dense’ [and] considered by officials in his presidency to be almost illiterate.

After his first wife's death in March 1906 he married secondly Eleanor, younger daughter of Matthew Arnold and widow of Armine Wodehouse, on 5 July 1909.