Jean Mayer (19 April 1920 – 1 January 1993) was a French-American scientist best known for his research on the physiological bases of hunger and the metabolism of essential nutrients, and for his role in shaping policy on world hunger at both the national and international levels. As a professor at the Harvard School of Public Health, Mayer directed a laboratory that did groundbreaking work on the hypothalamic regulation of obesity and various metabolic disorders. In 1968-69, having worked as an adviser to the World Health Organization and UNICEF, he was appointed principal organizer and chair of the first White House Conference on Food, Nutrition, and Health. At Harvard University, he served as Master of Dudley House before leaving in 1976 to become the tenth President of Tufts University in Medford, Massachusetts, where he is given credit for having brought about an unprecedented rise in the university's national reputation. He died unexpectedly on January 1, 1993.

Mayer was born in Paris in 1920 into a distinguished French scientific family. His father, André Mayer, was a celebrated physiologist at the Collège de France, his mother an outstanding doctoral student in André Mayer's laboratory when they met. Jean Mayer's sister, Dr. Geneviéve Massé would become a Professor of Biostatistics at the French National Superior School of Public Health.

Mayer worked in his father's laboratory as a schoolboy, while devoting the greater part of his intellectual energies to mathematics—differential and integral calculus, analytical geometry, series and functions, and theoretical physics. He later made extensive use of mathematical models in his work on the physiology of hunger and nutrition. At age nineteen, he was admitted to the École Normale Superieure as one of only 20 science students from all of France. At the outbreak of World War II, he had earned a bachelor's degree in Philosophy (summa cum laude), a bachelor's degree in Mathematics (magna cum laude), and a master's degree in Physics and Chemistry.

With France's declaration of war on Germany in 1939, Mayer enlisted in the Ecole Normale Superieure Artillery Training Unit. In 1940, his was one of the units that provided a protective ring around the British expeditionary force on the beaches during the Dunkirk evacuation, gaining time for the evacuation of the British Expeditionary Force (BEF) across the English Channel. Taken prisoner by the Germans, Mayer shot a guard and managed a narrow escape, making his way to southern France. A Free French sympathizer with a high position in the Vichy government secretly supplied him with a passport and papers permitting his escape to Algeria, Morocco, Martinique and Guadeloupe. He would eventually make his way to the United States, where his father, who immediately before the outbreak of war had been invited to give the Lowell Lectures at Harvard, was in Cambridge, Massachusetts, with Mayer's mother and sister. On his visit to them Mayer met Elizabeth Van Huysen, who would become his wife.

By the end of 1941, Charles de Gaulle had formed the Free French as an army and government in exile. Mayer reenlisted in the Free French Forces, at first serving as a gunnery officer on convoy duty in the North Atlantic. When one convoy was forced back by weather and U-Boat attacks into harbor at Halifax, Nova Scotia, Elizabeth Van Huysen came up to Halifax from Boston and the two were married. They had a honeymoon of less than 24 hours before the convoy sailed again. Mayer would not return to America until 1945.

In North Africa, Mayer served as commander of an artillery battery in the Colonial and Marine First Free French Division that accompanied the British Eighth Army at the second battle of El Alamein, following its victory there with a long advance into Libya and Tunisia. With the Tunisian campaign completed, he was detached to the staff of the War Ministry in Algeria, received training in ship-to-shore attacks and landings, and landed with the First Free French Division—by then part of the U.S. Fifth Army—south of Naples.

Mayer had been awarded the Croix de Guerre for his escape from German captivity. At the Battle of Monte Cassino in the Italian campaign, he would be awarded another for risking his life as forward observer of the heavy (155mm howitzer) battalion. After the D-Day landings, he would land in the south of France to command a Free French infantry regiment—made up largely of boys too young to have been drafted for forced labor in Germany and older men who had served in World War I—in the Colmar Pocket, managing to hold the line along the Vosges against attack by the elite Hermann Goering SS Division. He would emerge from this campaign with two palms to his Croix de Guerre, the Resistance Medal, and the Legion of Honour, and from the war with 14 decorations in all.

At war's end, Mayer joined his wife in the United States and received a small grant from the Rockefeller Foundation for graduate work in physiological chemistry. He elected to attend Yale, which had a leading faculty—among them C.N.H. Long, Abraham White, John Fulton, Donald Barron and Desmond Bonnycastle—in his area of interest. Mayer would later recall that, as a military veteran and son of a distinguished French physiologist, he was accepted by the faculty as a junior colleague, being made a member of the Faculty Club and put in charge of the biochemistry laboratory where medical students performed practical exercises. The salary of eighteen hundred dollars turned out to be crucial to his household income when his first son, André, the first of five Mayer children, was born in 1946.