William Gillies (1865–1932) was a Scottish patriot and a socialist. He helped to form the Scots National League which joined with other bodies to form the National Party of Scotland which in turn evolved into the Scottish National Party (SNP).
Gillies was born in the Galloway region of Scotland in 1865, but grew up in London. He was interested in Scottish History from an early age and at the age of seventeen he became friend to John Murdoch who was then the editor of The Highlander. Gillies became as enthusiastic for the rights of crofters in the Scottish highlands and joined the Highland Land League. He was at this stage enthusiastic for some form of home rule for Scotland within the United Kingdom but grew to support Scottish independence instead.
Gillies also began to learn Gaelic and wrote a number of plays in the language, also serving as secretary of the Gaelic Society of London from 1904 to 1905. However he stood down as secretary when the society rejected his proposal that they should campaign to make Gaelic the national language of Scotland.
Gillies, encouraged by Murdoch, also became aware of the developments in the politics of Ireland becoming an ardent supporter of Sinn Féin, associating with prominent figures such as Art O'Brien who would become the head of the Irish Self Determination League. He supported the Easter Rising of 1916 and was deeply critical of those socialists who refused to support it, along with those in the Scottish Gaelic revival circles who refused to support it.