James Buchanan (1804–1870) was a Scottish minister and theologian. He joined the Free Church of Scotland in 1843, and succeeded Thomas Chalmers as professor of systematic theology at the New College of the Free Church in Edinburgh in 1847, a post he held for twenty-one years. Buchanan's magnum opus was The Doctrine of Justification, which still has great value as a classic treatment of the article by which Martin Luther says the church stands or falls. He covers biblical, systematic, and historical ground in his work, but is never far from a warm-hearted evangelical delight in the doctrines he is expounding.