Sigmund Freud (born Schlomo Sigusmund Freud) was born on May 6, 1856 in the village of Freiberg, Moravia (now part of the Czech Republic) into a Jewish merchant family. When he was four years old, his family moved to Vienna, where Freud remained until the Nazi invasion and occupation in 1938.

The ethnic tensions, class conflicts, and intellectual energy in Vienna at the end of the nineteenth century informed Freud's daily life. At the time, the city was a laboratory for radical innovations in politics, philosophy, and the arts and sciences. A well-educated and ambitious young man immersed in classical literature and philosophy, Freud began his education in 1873 at the University of Vienna. Freud was initially interested in law, then zoology, and later neurology. He pursued a fellowship in this last field, traveling to Paris to work with Jean-Martin Charcot. Charcot pioneered the study of hysteria, and also pursued an interest in hypnotic states. Freud found both areas of study extremely interesting. Under Charcot's direction, he turned definitively from mainstream medical studies to the nascent, speculative field of psychology.

In 1886, Freud returned from academic study in Paris to Vienna, where he opened a private practice specializing in nervous and brain disorders. That same year, he married Martha Bernays, with whom he had six children during the span of nine years. Over the next decade, Freud combined clinical practice with theoretical insights to develop the foundational principles of psychoanalysis. In 1899, he introduced the results of his investigations to a wider audience with the publication of The Interpretation of Dreams. The essence of his theory stipulated that all dreams involve a condensation and displacement of psychological events past and present: in other words, the mind works to reconfigure conscious and unconscious memories in seemingly cryptic, but ultimately illuminating and meaningful ways.

In 1902, Freud was appointed associate professor at the University of Vienna, where he collaborated with other like-minded professionals to found the Vienna Psychoanalytic Society in 1908. During these years, Freud continued to write many seminal essays, including Three Essays on the Theory of Sexuality (1905), in which he develops his theory of the Oedipus complex and its role in sustaining the everyday drives and passions of men.

World War I brought the burgeoning movement of psychoanalysis to a virtual halt, with doctors and practicing clinicians unable to circulate their research or convene to exchange new ideas. Freud himself had three sons fighting in combat, and nervously awaited the outcome of the international conflict. Far from lapsing into an unproductive glut, however, Freud capitalized on this tense period in his own life to formulate the concept of competing life and death drives, later formalized in Beyond the Pleasure Principle (1923).

At the pinnacle of his career, Freud was diagnosed with oral cancer, which left him in a state of perpetual pain and discomfort. The difficulties of continuing his work in poor health were compounded by the political climate of Europe in the 1930s. Freud was shocked to witness the electoral rise of the Nazi Party, which developed an increasingly strong presence in Austria throughout the decade. Freud was frightened into leaving the country after his daughter Anna was summoned to the local Gestapo headquarters, though she was later released without harm. In 1938, he took refuge in Paris with the help of Princess Marie Bonaparte. Freud later moved to London, where he prevailed upon his doctor and friend, Max Schur, to assist in his suicide. Freud died of a morphine overdose in London on September 23, 1939.

Freud has always been a controversial figure, both in the clinical and academic arenas. No sooner had he elaborated his central theories at the turn of the century than various factions within the Vienna school broke off to practice their own interpretations of Freudian psychoanalysis. One of his most famous prodigal disciples is Carl Jung, who extended Freud's insights in innovative directions, and continued publishing his own essays on psychoanalysis after Freud's death. In France, Jacques Lacan became another devoted disciple. Beginning in the early 1950s, he undertook a comprehensive reinterpretation of Freud's oeuvre in a series of seminars that would later be transcribed to constitute the theoretical foundation of an "ecole freudienne" in Paris. The widespread revival of Freud's work and reputation in the postwar years was followed by a period of intense scrutiny and critique in the 1970s, particularly by American feminists dismayed at Freud's insensitive treatment of women and female sexuality. Freud's most controversial case in this regard involved a "hysterical" teenage patient named Dora, whose allegations of sexual abuse against a family friend were repeatedly dismissed as her own repressed fantasy.

Nevertheless, the extent of Freud's influence on popular conceptions of human psychology cannot be overstated. Indeed, our notions of identity, memory, childhood and sexuality have often been conceived in relation to—and in opposition to—Freud's work. Many psychoanalytic terms coined by Freud have crossed over into everyday language, such as "repression," "the unconscious," "Oedipus complex," "death drive," and "penis envy." Despite the pervasiveness of his cultural influence, there are relatively few self-proclaimed "Freudian" analysts still practicing in the United States outside of New York City. In many European countries, by contrast, Freudian (and other derivative models of) psychoanalysis continue to enjoy widespread credibility and practice.

In addition to his formative influence in the study of human psychology and clinical psychoanalysis, Freud's ideas have been highly important to literary criticism. In fact, many of the theories developed in his lectures and writings often reference works of literature, from the ancient Greek playwright Sophocles' Oedipus Rex, to Shakespeare's Hamlet, to Goethe's Faust. This is partly because Freud believes that dreams operate through mechanisms of condensation and displacement that resemble literary representation, and partly because he believes that creative writers get their source material from the inspirations of the unconscious.