Alexander Barclay (May 21, 1810 – December 1855) was an American frontiersman. After working in St. Louis as a bookkeeper and clerk, he worked at Bent's Old Fort. He then ventured westward where he was a trapper, hunter, and trader. Barclay entered into a common-law relationship with Teresita Sandoval, one of the founders of the settlement and trading post El Pueblo. He helped settle Hardscrabble, Colorado and built Fort Barclay in New Mexico.