Joseph Henry Keenan (August 24, 1900 – July 17, 1977) was an American thermodynamicist and mechanical engineer noted for his work in the calculation of steam tables, research in jet-rocket propulsion, and his work in furthering the development in the understanding of the laws of thermodynamics in the mid 20th century. His classic 1941 textbook Thermodynamics served as a fundamental teaching tool in various engineering curricula during the 1940s and 1950s. This shows that the second law of thermodynamics can be stated in terms of the existence of stable equilibrium states.