Existentialism is a philosophical movement that deals with human freedom. Existentialism itself is a revolt against traditional philosophy; it has been labeled a philosophy but a definition is difficult as its proponents have a marked difference in outlook. Existentialist thought concerns itself with trying to understand fundamentals of the human condition and its relation to the world around us. Basic questions include, 'what is it like to be a human in the world?' and 'what is the nature of human freedom?'.

Existentialism can be seen as a philosophical movement that rejects the belief that life has an inherent meaning, but instead requires each individual to posit his or her own subjective values. Existentialism, unlike other fields of philosophy, does not treat the individual as a concept, and values individual subjectivity over objectivity. As a result, questions regarding existence and subjective experience are seen as being of paramount importance, and initially above all other scientific and philosophical pursuits.

There are several philosophical positions, all related to existential philosophy, but the main identifiable common proposition is that existence precedes essence, i.e. that a human exists before his or her existence has value or meaning. Humans define the value or meaning of both his or her existence and the world around him or her in his or her own subjectivity, and wanders between choice, freedom, and existential angst. Existentialism often is associated with anxiety, dread, awareness of death, and freedom. Famous existentialists include Sartre, Nietzsche, Kierkegaard, Heidegger, Camus (although he defines himself as an absurdist and disagreed with a lot of Sartre's ideas), Fanon, Miguel de Unamuno y Jugo, and Simone de Beauvoir.