Ralph Edward Oesper (14 June 1886 – 10 December 1977) was an American chemist and historian of chemistry. He is noted for his biographies of scientists, emphasizing their personal lives in addition to their scientific contributions. Oesper translated significant works in the field of chemistry to various languages especially English. As an independent investigator, he developed improved analytical methods. These contributions included new reagents for certain types of titrations. One such new reagent, Oesper's Salt, is named for him.