William Rankine Milligan, Lord Milligan PC, KC (12 December 1898 – 28 July 1975) was a Scottish Tory politician and judge.

Educated at Sherborne School, University College, Oxford, and the University of Glasgow, he served with the Highland Light Infantry from 1917 to 1919. He was admitted as an advocate in 1925, and appointed a King's Counsel in 1945.

He was an unsuccessful parliamentary candidate at Central Ayrshire in 1950 and 1951, and was elected for Edinburgh North in 1955, where he served until 1960.

He was appointed Solicitor General for Scotland from 1951 to 1954, and Lord Advocate from 1954 to 1960, and was made a Privy Counsellor in 1955. He was appointed to the bench in 1960, with the judicial title Lord Milligan. He retired in 1973.

He was a member of the Royal Company of Archers.