John Horne PRSE FRS FRSE FEGS LLD (1 January 1848 – 30 May 1928) was a Scottish geologist. He served as President of the Royal Society of Edinburgh from 1915 to 1919.
Horne was born on 1 January 1848, in Campsie, Stirlingshire, the son of James Horne of Newmill and his wife Janet Braid. John was educated at the High School, Glasgow, and Glasgow University.
He joined the Scottish Branch of HM Geological Survey in 1867 as an assistant and became an apprentice to Ben Peach. The two soon became good friends and collaborators. Horne was involved in mapping the Central Lowlands. Horne was a logical thinker and writer, complementing Peach's skills of resolving the internal structure of mountains by looking at the surface rocks. After their work in the Highlands, Horne and Peach wrote 'Northwest Highlands Memoir' in 1907. The work is regarded as one of the most important geological memoirs. Horne wrote most of the memoir himself. From 1901 until 1911, John Horne was the Director of the Scottish Branch of the Survey.
Horne was elected a Fellow of the Royal Society of Edinburgh in 1881, upon the proposal of Sir Archibald Geikie, Sir Charles Wyville Thomson, Peter Tait and Robert Gray, and won the Society's Neill Prize for 1889-92. Horne was very active in the affairs of the RSE and served as Councillor (1902-5; 1906-7; 1914-15), Vice-President (1907-13) and President (1915-19).