William Lindsay Alexander FRSE (24 August 1808 – 20 December 1884) was a Scottish church leader.
He was born in Leith, the son of William Alexander, a wine merchant, and Elizabeth Lindsay.
He was educated at Leith High School then the universities of St Andrews and Edinburgh, where he gained a lasting reputation for classical scholarship. He entered Glasgow Theological Academy under Ralph Wardlaw in September 1827, but in December of the same year he left to become classical tutor at the Blackburn Theological Academy, afterwards the Lancashire Independent College, in north-west England. He stayed at Blackburn until 1831, lecturing on biblical literature, metaphysics, Greek and Latin.
After short visits to Germany and London, he was invited back to Edinburgh in November 1834 to become minister of North College Street church (afterwards Argyle Square), an independent church which had arisen in 1802 out of the evangelical movement associated with the Haldane brothers, Robert and James. When the church sold its property to the government to make way for the National Museum of Scotland, Alexander's congregation worshipped in the Queen Street Hall until 1861 when the new church was completed on George IV Bridge, renamed Augustine Church because of Alexander's strong, albeit independent Augustinian influence in his sermons. He deliberately put aside the ambition to become a pulpit orator in favour of the practice of biblical exposition, which he invested with charm and impressiveness.
Alexander took an active part in the "voluntary" controversy which ended in the Disruption of 1843, but he also maintained broad and catholic views of the spiritual relations between different sections of the Christian church. In 1845 he visited Switzerland with the special object of inquiring into the religious life of the churches there. In 1845 he received the degree of Doctor of Divinity (D.D.) from the university of St Andrews.