Reese James Llewellyn was a Welsh-American businessman. He was the co-founder and president of Llewellyn Iron Works, a company based in Los Angeles, which provided iron works and steel for the construction of buildings in Southern California, the Western United States, Mexico, and South America. The company also produced steel from iron ore and during the World War I shipbuilding boom it was one of the largest manufacturers of triple-expansion steam engines on the West Coast.