Portal:History of science/Selected anniversaries/July 20
- 1822 - Birth of Gregor Mendel, German scientist, father of modern genetics (d. 1884)
- 1866 - Death of Bernhard Riemann, German mathematician (b. 1826)
- 1876 - Birth of Otto Blumenthal, German mathematician (d. 1944)
- 1897 - Birth of Tadeus Reichstein, Polish-born chemist, Nobel Prize in Physiology or Medicine laureate (d. 1996)
- 1909 - Birth of Jean Focas, Greco-French astronomer (d. 1969)
- 1922 - Death of Andrey Markov, Russian mathematician (b. 1856)
- 1947 - Birth of Gerd Binnig, German-born physicist, Nobel laureate
- 1960 - The Polaris missile is successfully launched from a submarine, the USS George Washington, for the first time