Celebrations are being held to mark the 150th birthday of Sigmund Freud, seen as the father of psychoanalysis.
Freud's theories also had an impact on art, literature and anthropology
Events are being staged in Vienna - where Freud spent most of his life - and in London, where he was forced to flee from the Nazis in 1938.
But the Viennese celebrations are said to be muted compared to those planned for Mozart's 250th anniversary.
Freud is credited with developing theories mapping the human mind and its links to the unconscious.
His theories are said to have influenced the fields of art, literature, anthropology and religion.
In Vienna, exhibitions, lectures and film festivals are being held.
Vienna's Sigmund Freud Museum, where he lived and had his practice, is opening an exhibit on the couch, a piece of furniture which has become almost synonymous with Freud and psychoanalysis.
However, the celebrations are subdued in comparison to the festivities for Mozart year, the BBC's Bethany Bell says.
Originally the Sigmund Freud Foundation had hoped that a soiree on Freud would be held at the Volksoper Opera house in Vienna on 5 May.
But the Volksoper decided to stage yet another performance of Mozart's opera The Magic Flute, our correspondent says.
Sigmund Freud was born in Moravia in what is now the Czech Republic in 1856.
Freud was forced to flee to London after Austria was annexed by the Nazis in 1938.
However, his time in London was short-lived and he died in London in 1939.