William Mackie FRSE DPH LLD (1856–1932) was a Scottish physician and public health specialist, remembered for his contributions to geology.
He spent most of his life in the Elgin area, first as a GP and then as Medical Officer of Health.
In 1904, Mackie proposed a basic theory for plate tectonics in a lecture to the Elgin Institute, "The Origin of Oceans and Continents".
From 1910 to 1913 he did extensive studies of the Rhynie area in Aberdeenshire and was the first person to discover plant-bearing cherts.
Aberdeen University awarded him an honorary doctorate (LLD) for his contributions to Geology in 1923.