Famous existentialists include Fyodor Dostoevsky , Jean-Paul Sartre , Friedrich Nietzsche , SÃ ren Kierkegaard , Samuel Beckett , Martin Heidegger , Albert Camus ( although he did not think of himself as an existentialist and had his own Theory of the Absurd ) , and Simone de Beauvoir . Existentialism is foreshadowed most notably by 19th century philosophers SÃ ren Kierkegaard and Friedrich Nietzsche , though it had forerunners in earlier centuries . In the 20th century , the German philosopher Martin Heidegger ( starting from Husserl 's phenomenology ) influenced other existentialist philosophers such as Jean-Paul Sartre , Simone de Beauvoir and ( absurdist ) Albert Camus .