"Know yourself" is a principle that many theosophists, even before Socrates, have emphasized upon it. But, the philosophers' approach to this principle is different from that of mystics. According to the philosophers, the self is nothing but the soul in a genera concept (al-nafs); so for them, self-knowledge is known as a kind of psychology, a branch of knowledge among others. But for the mystics, especially for Ibn 'Arabi, the real Self is much deeper than the soul, and self-knowledge is the ultimate goal of mysticism.This paper will address the following questions from Ibn 'Arabi's point of view:1-What is the source of this principle: "Know yourself"? 2-What does it entail in terms of a goal? 3-What is meant by self in it? 4-What is meant by knowledge? 5-How can we know ourselves?In this paper, the importance of self-knowledge in Ibn 'Arabi's philosophy, the reliability of the two above mentioned hadiths for him, and his different interpretations of them will be discussed in the context of his theory of oneness of Being (wahdat al-wujud). Also, "fanaa" which is the result of self-knowledge will be discussed from Ibn 'Arabi's point of view and his understanding of this term will be compared with the doctrine of the annihilation, according to other philosophical and mystical traditions.