Admiral William Alexander Baillie-Hamilton (6 June 1803 – 1 October 1881) was a Scottish naval commander who served as Second Secretary to the Admiralty from 28 April 1845 to 22 May 1855.

A member of the Baillie-Hamilton family headed by the Earl of Haddington, he was the son of the Venerable Charles Baillie, Archdeacon of Cleveland and his wife Lady Charlotte Home, daughter of Alexander Home, 9th Earl of Home.

A gravestone with the names inscribed of William Alexander Baillie-Hamilton's and that of his wife, Harriet, lies in Greyfriars Churchyard, Edinburgh.

He is listed as having died in Portree, on the Isle of Skye.

[1] His son, also William (1844–1920), played football for Scotland in the first of the England v Scotland representative football matches (1870–1872) and was later a senior civil servant.