John Stuart Stuart-Glennie (1841–1910) was a Scottish barrister, socialist and folklorist.
John S. Stuart-Glennie was the son of the daughter of John Stuart of Inchbreck, Professor of Greek in the University of Aberdeen; his father was Alexander Glennie of Maybank Aberdeen. He was educated in law at the University of Aberdeen and became a barrister, called to the bar at the Middle Temple in 1853. He later undertook a series of journeys of historical exploration across Europe and Asia to collect folklore.
In 1885 Stuart-Glennie met and befriended George Bernard Shaw in London at the house of Jane Wilde, known as "Speranza". He took part in a socialist demonstration in Trafalgar Square, in 1887. He clashed with Annie Besant in wanting to include family matters in the charter of the Social Democratic Federation during the 1880s; and was later a Fabian for a time, before coming up against the same issue of women's rights as foundational. Socialist views led him in 1906 to predict a Russian revolution and transformation of Europe.
Stuart-Glennie was involved in the attempt to set up a Celtic League in 1886, and in Scottish activism of the 1890s.Patrick Geddes was influenced by his pan-Celticism.
In his time Stuart-Glennie was seen, by Bernard Shaw, as a successor to Henry Buckle, with a theory of religious origins going back some eight thousand years, and based on racial foundations.Lewis Mumford in a 1956 work credited him with anticipating the Axial Age concept. As a disciple of Buckle, with whom he travelled, Stuart-Glennie was heavily criticised by John Mackinnon Robertson in Buckle and His Critics; Robertson took up challenges to his account of Buckle in Pilgrim Travels, made in the biography by Alfred Huth, was dismissive as callow of the theories about the era of 600 BC, and discounted John Fiske as a supporter of Stuart-Glennie.