Lieutenant General Sir William Pitcairn Campbell, KCB (20 June 1856 – 22 September 1933) was a British Army general during the First World War.

Pitcairn Campbell was the son of James Pitcairn Campbell and his wife, Eleanor (née Eyre), of Burton Hall, Neston. He had two elder sisters, Eliza and Georgina. He was educated at Windlesham House School, Eton College and the Royal Military College, Sandhurst.^[1][2]

Pitcairn Campbell was commissioned into the King's Royal Rifle Corps in 1875.^[3] He served with the Mounted Infantry Camel Corps in Sudan between 1884 and 1885.^[3][4] His battalion served in South Africa from 1899 to 1901 during the Second Boer War. At the Battle of Talana Hill he was wounded and his commanding officer was killed. As second in command, he took command of his battalion and was part of the garrison besieged at Ladysmith.^[4] He was subsequently promoted to lieutenant colonel in command of the 1st Battalion on 25 January 1900.^[3][5]

Pitcairn Campbell was aide-de-camp to King Edward VII from 1900 to 1907 and was appointed a Companion of the Order of the Bath in the King's Birthday Honours of 1906.^[1][6] He was appointed commander of the 3rd Brigade in 1904 and General Officer Commanding 5th Division in 1909.^[3] He moved on to be General Officer Commanding-in-Chief of Southern Command from 1914 and General Officer Commanding-in-Chief of Western Command from 1916; he retired in 1918.^[3]

Pitcairn Campbell was knighted in 1915 on promotion to Knight Commander of the Order of the Bath.^[7][4] In 1916, he was appointed Colonel of the Highland Light Infantry, succeeding General Sir Henry Hildyard.^[8][9]

In 1888 a fellow infantry officer, Major Gilbert, who had been serving in India, named Pitcairn Campbell as co-respondent in the divorce case against his wife. The following year, he and Edith Gilbert (née Prothero) married and went on to have one daughter.^[10][11]