Brigadier-General Alfred Douglas Miller CBE DSO (1 March 1864 − 5 December 1933) was a British army officer.
Miller was commissioned a lieutenant in the 2nd Dragoons (Royal Scots Greys) on 7 February 1885, and was promoted to the rank of captain on 28 June 1893. He was adjutant of the Royal Scots Greys from 1896 to 1900. With the outbreak of the Second Boer War he was chief staff officer to Sir John French, and on 24 December 1901 he was appointed a Deputy-Assistant Adjutant-General on the staff in South Africa. He was promoted major on 20 February 1902. For his service in the war, he was mentioned in despatches (dated 8 April 1902), and received the Distinguished Service Order (DSO) in the South Africa Honours list published on 26 June 1902.
He led the 2nd Dragoon Regiment (Royal Scots Grey) from 1907 to 1911, as a lieutenant colonel, was promoted to colonel in 1911, and ultimately reached the rank of brigadier-general. He was appointed a Commander of the Order of the British Empire in the 1919 New Year Honours.
Miller married Ella Fletcher in 1899, and they had five children. He died in England on 5 December 1933.