Daniel Kahneman (/ˈkɑːnəmən/; Hebrew: דניאל כהנמן; March 5, 1934 – March 27, 2024) was an Israeli-American psychologist best known for his work on the psychology of judgment and decision-making as well as behavioral economics, for which he was awarded the 2002 Nobel Memorial Prize in Economic Sciences together with Vernon L. Smith. Kahneman's published empirical findings challenge the assumption of human rationality prevailing in modern economic theory. Kahneman became known as the "grandfather of behavioral economics."

With Amos Tversky and others, Kahneman established a cognitive basis for common human errors that arise from heuristics and biases, and developed prospect theory. In 2011, Kahneman was named by Foreign Policy magazine in its list of top global thinkers. In the same year, his book Thinking, Fast and Slow, which summarizes much of his research, was published and became a best seller. In 2015, The Economist listed him as the seventh most influential economist in the world.

Kahneman was professor emeritus of psychology and public affairs at Princeton University's Princeton School of Public and International Affairs. Kahneman was a founding partner of TGG Group, a business and philanthropy consulting company. He was married to cognitive psychologist and Royal Society Fellow Anne Treisman, who died in 2018.

Daniel Kahneman was born in Tel Aviv, in the British Mandate of Palestine (now Israel), on March 5, 1934 while his mother Rachel (née Shenzon) was visiting her family. His parents were Lithuanian Jews who had emigrated to France in the early 1920s; his paternal uncle was Rabbi Yosef Shlomo Kahaneman, the head of the Ponevezh Yeshiva. He spent his childhood years in Paris. Kahneman and his family were in Paris when it was occupied by Nazi Germany in 1940. His father, Efrayim, was picked up in the first major round-up of French Jews, but he was released after six weeks due to the intervention of his employer, La Cagoule backer Eugène Schueller. The family was on the run for the remainder of the war but survived except for Efrayim who died of diabetes in 1944. Kahneman and his family then moved to Mandatory Palestine in 1948, just before the creation of the state of Israel.

Kahneman wrote of his experience in Nazi-occupied France, explaining in part why he entered the field of psychology:

It must have been late 1941 or early 1942. Jews were required to wear the Star of David and to obey a 6 p.m. curfew. I had gone to play with a Christian friend and had stayed too late. I turned my brown sweater inside out to walk the few blocks home. As I was walking down an empty street, I saw a German soldier approaching. He was wearing the black uniform that I had been told to fear more than others – the one worn by specially recruited SS soldiers. As I came closer to him, trying to walk fast, I noticed that he was looking at me intently. Then he beckoned me over, picked me up, and hugged me. I was terrified that he would notice the star inside my sweater. He was speaking to me with great emotion, in German. When he put me down, he opened his wallet, showed me a picture of a boy, and gave me some money. I went home more certain than ever that my mother was right: people were endlessly complicated and interesting.

— NobelPrize Bio 2002

In 1954, Kahneman received his Bachelor of Science degree, with a major in psychology and a minor in mathematics, from the Hebrew University of Jerusalem. Israeli intellectual Yeshayahu Leibowitz, whom Kahneman describes as influential in his intellectual development, was Kahneman's chemistry teacher at Beit-Hakerem High School, and Kahneman's physiology professor at university. Kahneman was average in mathematics, but he thrived in psychology. Kahneman was led to psychology when he discovered in his teens that he was more interested in why people believe in God than in whether God exists, and more interested in indignation than in ethics.