The phenomenon of spirit is a topic discussed frequently by Jung throughout his writings although spirit is not always considered to be central to the practice of analytical psychology. This article points to the importance of spirit in analytical psychology by presenting a survey of Jung's discussions of spirit. In Jung's discussions, spirit is not treated as an abstract concept but as an empirical phenomenon: to Jung, spirit is a psychological reality that can be described and whose effects can be experienced. Spirit is both described as an archetype and as a component of all archetypes. Spirit is related to the principle of life itself and is a prerequisite of both personal and cultural development and transformation. The article documents how Jung's understanding of spirit developed over time and in relation to different topics: Freud's psychoanalysis, the Red Book, fairy-tales, Christianity, Nietzsche's book on Zarathustra, Germany in the 1930's, alchemy, and creative work. The paper concludes with a discussion of the relevance of spirit to clinical practice.