Joseph Reynolds (June 11, 1819 – February 21, 1891) was an American entrepreneur and founder of the Diamond Jo Line, a transportation company which operated steamboats on the upper Mississippi River. In his youth, while still living in upstate New York, he operated a butchery, a general store, a grain mill, and a tannery.
Reynolds established a successful leather-tanning operation in Chicago before becoming a grain trader in the upper-Mississippi River corridor. He acquired his own steamboats in order to improve access for his own grain shipments, and he eventually expanded to haul freight on the Mississippi River for other shippers. This fleet of river steamers grew into a company called the Diamond Jo Lines. He developed the Hot Springs Railroad in Arkansas. As a legacy, he established an endowment for the University of Chicago in order to build a clubhouse: the Reynolds Club, most recently used as a student union.