Henri Tajfel (born Hersz Mordche Tajfel; 22 June 1919 – 3 May 1982) was a Polish social psychologist, best known for his pioneering work on the cognitive aspects of prejudice and social identity theory, as well as being one of the founders of the European Association of Experimental Social Psychology.

Tajfel grew up in Poland. Because of Polish numerus clausus restrictions on Jews in university education ^{[citation needed]}, he left Poland to study chemistry at the Sorbonne in France. At the outbreak of World War II, he volunteered to serve in the French army. A year later, he was taken prisoner-of-war by the Germans. He faced a dilemma: whether or not to admit to the Germans that he was a Polish Jew. He claimed to be a French citizen but did not deny his Jewish identity. He reasoned that if he denied being Jewish and if the Germans found out later that he was Jewish, he would certainly have been killed. In the event, Tajfel survived the war in a series of prisoner-of-war camps.

On his return home he discovered that none of his immediate family, and few of his friends, had survived the Nazi Holocaust. He was to write later about the profound effect that this had on him and how it led to his later work on the psychology of prejudice and intergroup relations.

After the war Tajfel worked for a series of relief organisations including the Œuvre de secours aux enfants (OSE), a Jewish humanitarian organisation. Tajfel's work with OSE involved resettling Jewish children, many of whom were orphans who had lost all their family. Tajfel would often say that his work with OSE was the most important achievement in his life and he kept in touch with many of the children whose lives he helped to rebuild. He also worked for the United Nations International Refugee Organization.

He was granted French citizenship in 1946. However, he was soon to meet his future wife Anna-Sophie Eber (Ann), who had been born in Germany but had moved to Britain before the Second World War. Henri and Ann set up home in Britain where their two sons, Michael and Paul, were born. Henri took on British citizenship (for details, see the biography in the Oxford Dictionary of National Biography).

In 1951 Tajfel began studying psychology at Birkbeck College, University of London. He won a competitive scholarship for mature students with an essay on the subject of prejudice. In 1954 he graduated and worked as a lecturer, first at the University of Durham and then at Oxford. In 1962 he was made a Founding Fellow of Linacre College, Oxford. In his research work at the University of Oxford, Tajfel examined several different areas of social psychology, including social judgement, nationalism, and, most importantly, the cognitive aspects of prejudice.

In 1967 he was made Chair of Social Psychology at the University of Bristol. At Bristol he conducted research into intergroup relations and was active in making Bristol University a European centre for social psychology. He retired from Bristol and moved back to Oxford shortly before his death from cancer in 1982.

Tajfel's early research at University of Durham and University of Oxford involved examining the processes of social judgement. He believed that the cognitive processes of categorization contributed strongly to the psychological dimensions of prejudice, which went against the prevailing views of the time. Many psychologists assumed that extreme prejudice was the result of personality factors, such as authoritarianism. According to this perspective, only those with personalities that predisposed them to prejudice were likely to become bigots. Tajfel believed this was mistaken. He had seen how large numbers of Germans—not just those with particular personalities—had given their support to Nazism and had held extreme views about Jews. Nazism would not have been successful without the support of "ordinary" Germans. Tajfel sought to discover whether the roots of prejudice might be found in "ordinary" processes of thinking, rather than in "extraordinary" personality types.