The Louden Machinery Company was an American engineering, manufacturing and design company based in Fairfield, Iowa. Founded by William Louden, the company in its early years manufactured and sold the patented hay carrier that he invented in 1867. The company later expanded into a wide variety of farm equipment and, in 1906, began an Architecture Department that reportedly designed more than 25,000 barns from 1906 to 1939. During World War I, Louden's monorail equipment carrier began to be applied to industrial and military applications. By the 1920s, much of the company's revenues were derived from industrial applications of its monorail equipment carriers.
Several sites associated with the company have been listed on the National Register of Historic Places. These sites include the company's 1892 manufacturing facility in downtown Fairfield, several homes in and around Fairfield, and a number of barns in Iowa, Ohio and Michigan that were designed by the company's Architecture Department.