Alexander William Johnston (20 August 1869 – 15 June 1932) was a British-born soldier, businessman and politician. He was a member of the Legislative Council in Western Samoa from 1928 until his death in 1932.

Johnston was born in Edinburgh in 1869.^[1] He served in the British Army in India and South Africa,^[2] before being sent to New Zealand to work as a military instructor.^[1] In 1915 he was part of the first reinforcement contingent that arrived in Western Samoa during World War I. He was discharged from the military in 1920.^[1] After leaving the army, he became branch manager of the Burns Philp company in Saluafata district.^[1]

Johnston contested the 1926 elections to the Legislative Council, but was unsuccessful.^[3] However, in 1928 he was appointed to the Council by the Administrator to replace elected member Olaf Frederick Nelson,^[4] who had been deported.^[5] Prior to the 1929 elections, Johnston resigned from his nominated seat and stood for one of the elected seats. He was elected with the most votes, alongside Samuel Meredith.^[5]

Johnston died of pneumonia on 15 June 1932, and was given a military funeral.^[1]