Ernst Otto Fischer (November 10, 1918 – July 23, 2007) was a German chemist who won the Nobel Prize for pioneering work in the area of organometallic chemistry.

He was born in Solln, near Munich. His parents were Karl T. Fischer, Professor of Physics at the Technical University of Munich (TU), and Valentine née Danzer. He graduated in 1937 with Abitur. Before the completion of two years' compulsory military service, the Second World War broke out, and he served in Poland, France, and Russia. During a period of study leave, towards the end of 1941 he began to study chemistry at the Technical University of Munich. Following the end of the War, he was released by the Americans in the autumn of 1945 and resumed his studies, graduating in 1949.

Fischer worked on his doctoral thesis as an assistant to Professor Walter Hieber in the Inorganic Chemistry Institute, His thesis was entitled "The Mechanisms of Carbon Monoxide Reactions of Nickel(II) Salts in the Presence of Dithionites and Sulfoxylates". After receiving his doctorate in 1952, he continued his research on the organometallic chemistry of the transition metal and indicated with his lecturer thesis on "The Metal Complexes of Cyclopentadienes and Indenes". that the structure postulated by Pauson and Kealy might be wrong. Shortly after he published the structural data of ferrocene, the sandwich structure of the η⁵ (pentahapto) compound. He was appointed a lecturer at the TU in 1955 and, in 1957, professor and then, in 1959, C4 professor. In 1964 he took the Chair of Inorganic Chemistry at the TU.