Jacques Loeb was born in 1859. His father, sympathetic to the democratic institutions of France, reared his son to embrace both German and French culture. Loeb was orphaned at age 16 and later attended the University of Berlin and the University of Munich to study philosphy. He earned a medical degree in 1885 then spent a year in Berlin studying brain physiology, publishing the results of his research. His later research involved experiments on heteromorphosis and the depth migrations of animals.

Loeb married Anne Leonard, an American who had just received her doctorate in philology at the University of Zurich. In 1891, Loeb accepted a position at Bryn Mawr and moved to America to teach and continue his scientific investigations. He found the facilities insufficient, however, and moved to accept a position at the University of Chicago the following year. His work was at first largely concerned with tropisms and heteromorphosis, but he became deeply interested in the theory of Arrhenius and thus came to write his famous series of papers on the physiological effects of ions. A direct outgrowth of this was his discovery of artificial parthenogenesis and antagonistic salt action in 1899. In 1902 he was called to fill a similar chair at the University of California. In 1902 he was called to fill a similar chair at the University of California.

In 1910 Loeb moved to the Rockefeller Institute for Medical Research, where he headed a department created for him. Throughout most of these years Loeb spent his summers at the Marine Biological Laboratory in Massachusetts, performing experiments on various marine invertebrates. It was there that Jacques Loeb performed his most famous experiment, on artificial parthenogenesis. Loeb was able to cause the eggs of sea urchins to begin embryonic development without sperm. This was achieved by slight chemical modifications of the water in which the eggs were kept, which served as the stimulus for the development to begin.

Loeb became one of the most famous scientists in America, widely covered in newspapers and magazines. He was the model for the character of Max Gottlieb in Sinclair Lewis's Pulitzer-winning novel Arrowsmith, the first great work of fiction to idealize and idolize pure science. Mark Twain also wrote an essay titled "Dr. Loeb's Incredible Discovery," which urges the reader not to support a rigid general consensus, but instead be open to new scientific advances.

Loeb was nominated many times for the Nobel Prize but never won. He passed away in 1924 in Bermuda.