Alexander Lang Elder (18 April 1815 – 5 September 1885) was a businessman and politician in colonial South Australia.
Elder was the second son of George Elder of Kirkcaldy, Fife, Scotland, by Joanna Haddo, his wife, daughter of Alexander Lang, of Leith, Scotland, and brother of Sir Thomas Elder, was born at Kirkcaldy, and emigrated on the Minerva to South Australia, arriving in January 1840 in Adelaide, where he founded the well-known mercantile firm of Elders Limited, later Elder, Smith & Co., of Adelaide. He was a partner with Frederick Dutton in a 20,000 acres (8,100 ha) pastoral lease at Mount Remarkable in 1846.
He married Mary Eliza Austin, a daughter of Rev. John Baptist Austin, of South Australia on 8 April 1847.
He was elected by the West Adelaide district to the first mixed franchise Legislative Council in 1851, but resigned his seat on 30 March 1853, leaving for England, where he headed of the firm of A. L. Elder & Co., of London, until his death in London on 5 September 1885.