Max Wertheimer (Austrian German: [ˈvɛrthaɪ̯mɐ]; April 15, 1880 – October 12, 1943) was a psychologist who was one of the three founders of Gestalt psychology, along with Kurt Koffka and Wolfgang Köhler. He is known for his book Productive Thinking and for conceiving the phi phenomenon as part of his work in Gestalt psychology.

Wertheimer became interested in psychology and studied under Carl Stumpf at the University of Berlin. Wertheimer then went on to obtain his PhD in 1904 under Oswald Külpe, at the University of Würzburg and then began his intellectual career teaching at the Institute for Social Research at Frankfurt University. For a short time, he left Frankfurt to work at the Berlin Psychological Institute, but returned in 1929 as a full professor.

Wertheimer eventually joined the faculty of The New School in New York, a position he held until his death. One of Wertheimer's postdoc researchers was the American psychologist Abraham Maslow who greatly admired Wertheimer.

Max Wertheimer was born on April 15, 1880, in Prague, then part of Austria-Hungary. He was born to Wilhelm and Rosa Wertheimer, second to his brother Walter. Wilhelm Wertheimer was an educator and financier. Rosa Wilhelm, born Rosa Zwicker, had a rich classical education. The Wertheimers were active in the Jewish community in which they lived. The Wertheimer household was extremely intellectual, therefore Max received education from both his parents; he engaged in political and educational discussions at home, as well as taking piano and violin lessons. After he received one of Baruch Spinoza's books as a gift, he developed an interest in philosophy. He felt that he and Spinoza shared a culture and common traits.

Wertheimer began his formal education aged five, at a private elementary school maintained by the Piarist order of the Roman Catholic Church. It was not uncommon at this time for Jewish children in central Europe to receive educations from the Catholic Church. Aged ten, he graduated from the Piarist Grammar School and enrolled in the Royal Imperial New City German State High School, where he could expect to obtain a degree that would qualify him for admittance to a university. Due to the diverse courses offered by the university, he began to contemplate his future, and realized his deep fascination with philosophy. He first began to study law at Charles University, where he also explored philosophy, and other fields such as music, physiology, and psychology. After a year, Max left and enrolled in University of Berlin where he shifted his study to philosophy. At Berlin, Max was able to work in the company of figures such as Carl Stumpf, Friederich Schumann, Georg Elias Müller, and Erich von Hornbostel. Later on, in 1903, he gained his PhD from the University of Würzburg. There he completed research on the lie detector.

Max Wertheimer began his academic career at the Psychological Institute in Frankfurt, later to become the University of Frankfurt. From 1910 to 1916 he worked there and conducted pioneering experiments in the perception of motion and phi phenomenon. Wertheimer first founded his Gestalt theory before World War I, publishing his research on perception in "Experimental Studies on Motion Vision" in 1912. During World War I Wertheimer was a research psychologist with the Prussian Artillery Testing Commission, the center of which was located in the Bavarian Quarter of Berlin, close to Albert Einstein's house. Wertheimer's friendship with Einstein began at this time, in his visits he attempted to understand the Gestalt-like processes Einstein had used to conceive the theory of relativity. In the war years Wertheimer also became friends with physicist Max Born. After the war, Wertheimer united with Born and Einstein to negotiate the release of the rector and some professors at the University of Berlin who were being held by students and soldiers making socialist demands from the university.

After the war, he further advanced his Gestalt theory in collaboration with Wolfgang Köhler, Kurt Koffka, and others through the Weimar years. He left Frankfurt from 1916 to 1929 to work at the Berlin Psychological Institute. He gave lectures and pursued his research on perception and gestalt in the University of Berlin. In 1923, while teaching in Berlin, Wertheimer married Anna Caro (called Anni), a physician's daughter, with whom he had four children: Rudolf (who died in infancy, 1924), Valentin (1925–1978), Michael (1927–2022) and Lise (born 1928, Lisbeth Rosa). He returned to Frankfurt in 1929 as a full professor, where he stayed until 1933.

In 1933, the change in Germany's government convinced Wertheimer to leave Germany. Hearing Adolf Hitler's declarations, he felt his Jewish roots placed him in danger. The Wertheimer family joined other German emigrees and moved to the United States. The Wertheimers' emigration was arranged through the U.S. consulate in Prague, and he and his wife and their children arrived in New York harbor on September 13, 1933. The family became citizens as well; that's why Max Wertheimer is referred to as a German-American psychologist. Along with his move to America, Wertheimer accepted a professional position at age fifty-three at the New School for Social Research in New York City. The New School had been founded only fourteen-years before when he gained the opportunity to teach courses there, remaining at the New School for the last decade of his life. From 1934–1940, Wertheimer wrote four major papers, philosophical essays on the topics of truth, ethics, democracy, and freedom which are all commonly grounded on gestalt ideas of the whole and its parts, and the importance of looking at the "total situation."