He was born in Breslau, Germany and from 1886 until 1891 he studied at the University of Heidelberg under Robert Bunsen, at the University of Berlin in the group of A. W. Hoffmann, and at the Technical College of Charlottenburg (today the Technical University of Berlin) under Carl Liebermann. He married Clara Immerwahr in 1901. Before starting his own academic career he worked at his father's chemical business and in the Institute of Technology in Zürich with Georg Lunge. During his time in Karlsruhe from 1894 until 1911 he and Carl Bosch developed the Haber process, which is the catalytic formation of ammonia from hydrogen and atmospheric nitrogen under conditions of high temperature and high pressure. In 1918, he received the Nobel Prize in Chemistry for this work. The Haber-Bosch process was a milestone in industrial chemistry, because it divorced the production of nitrogen products, such as fertilizer, explosives and chemical feedstocks, from natural deposits, especially sodium nitrate ('Caliche'), of which Chile was a major producer. The sudden availability of cheap nitrogenous fertilizer is credited with averting a Malthusian catastrophe, or population crisis.
He was also active in the research of combustion reactions, the separation of gold from sea water, adsorption effects, and electrochemistry. A large part of his work from 1911 to 1933 was done at the Institute for Physical and Electrochemistry at Berlin-Dahlem. Haber played a major role in the development of chemical warfare in World War I. Part of this work included the development of gas masks with absorbant filters. Gas warfare in WWI was, in a sense, the war of the chemists, with Haber pitted against French Nobel laureate chemist Victor Grignard. His wife opposed his work on poison gas and committed suicide with his service weapon after he personally oversaw the first use of chlorine in Ypres.
In his studies of the effects of poison gas, Haber found a simple mathematical relationship between the concentration (C) of the gas and the amount of time (t) it was breathed in, expresed as C x t = k, where k is a constant. In other words, exposure to a low level of gas for a long time can cause the same result (e.g. death) as exposure to a high concentration for a short time. This relationship is known as Haber's rule. Haber defended gas warfare against accusations that it was inhumane, saying that death was death, by whatever means it was inflicted. In the 1920s, he developed the cyanide gas formualtion Zyklon B, which was used as an insecticide, especially as a fumigant in grain stores, and also later in the concentration camps.
Being Jewish, he was forced to emigrate by the Nazis in 1934. Haber was a patriotic German who was proud of his service in World War I, for which was decorated. He struggled to cope with the new reality that his enormous contributions to German industry were disregarded during his vilification by the Nazi regime. He died in exile in Basel after a grave illness.