William Philip Sidney, 1st Viscount De L'Isle (May 23, 1909 - April 5, 1991), 15th Governor-General of Australia, was the last British Governor-General. He was the son of the 5th Baron De L'Isle and Dudley, and came from one of England's oldest and most distinguished families. He was educated at Eton and Cambridge and became a chartered accountant. In 1929 he joined the Grenadier Guards Reserve of Officers. He was a son-in-law of Field Marshal Lord Gort, VC.

During World War II Sidney served in France and Italy. He led a handful of men in the defence of the Anzio beachhead, for which he was awarded the Victoria Cross.

His citation reads:

Sidney led a successful attack which drove German troops out of a gully. Later he led another counter-attack and dashed forward, engaging the Germans with his tommy gun at point-blank range, forcing a withdrawal. When the attack was renewed, Sidney and one guardsman were wounded and another killed, but he would not consent to have his wounds dressed until the Germans had been beaten off and the battalion's position was consolidated. During this time, although extremely weak from loss of blood he continued to encourage and inspire his men.

William Philip Sidney
1st Viscount De L'Isle

In 1944 he was elected unopposed to the House of Commons as Conservative MP for Chelsea. His father died in 1945 and he went to the House of Lords as the 6th Baron De L'Isle. In 1951 he was appointed Secretary of State for Air under Winston Churchill and held that office until 1955. During this time he visited Australia, travelling to Woomera to examine weapons research and meeting Prime Minister Robert Menzies, who was later to appoint him Governor-General. In 1956 he was created Viscount De L'Isle.

In 1961 De L'Isle was appointed Governor-General of Australia following the sudden death of Lord Dunrossil. He performed his ceremonial duties with dignity and travelled widely around Australia. There were no political or constitutional controversies during his term, since the Liberal government of Robert Menzies was firmly in power.

By the time of De L'Isle's retirement in 1965 public opinion was strongly in favour of an Australian Governor-General, although this was not a reflection on his performance in the role. His continuing interest in Australia was shown by several visits after his retirement, the last for Australia's bicentenary in 1988, when he presented a bronze statue which now stands in the grounds of Government House in Canberra. He died in Britain in April 1991.