The aim of this paper is to study Existential principality proposing a new concept. Kierkegaard and Heidegger’s Ideas as two important philosophers of Existential philosophy have been studied. Existential authenticity in Kierkegaard and Heidegger’s doctrine has been investigated by using of comparative analytical method. The results show the authenticity is not exactly equivalent with individuality, but the existential authenticity is a multidimensional concept which indicates to the human lifestyle. Kierkegaard, Heidegger and other philosophers of existence in addition to emphasizing individuality and its importance in mass society, mention another components of authenticity including authentic communication, evading from formal orientation and mediocrity, Accountability and care about Existential angst. Although there are certain differences between them, but in the most cases the meaning of authenticity is the same. Finally, by studying the components of authenticity, a concept of existential philosophy has been proposed in this paper.