Stepan Prokopovych Tymoshenko (, ) (December 22, 1878 – May 29, 1972), was a Russian and U.S. engineer of Ukrainian ethnicity. He is considered to be the father of modern engineering mechanics. A founding member of the Ukrainian Academy of Sciences, Timoshenko wrote seminal works in the areas of engineering mechanics, elasticity and strength of materials, many of which are still widely used today. Having started his scientific career in the Russian Empire, Timoshenko emigrated to Yugoslavia during the Russian Civil War and then to the United States.