The figure of the alchemical Mercurius features ubiquitously and radically in Jung's later works, but despite this, there has been little research concerning Mercurius in Jungian studies to date. In this book, Mathew Mather explores the figure of the alchemical Mercurius and contextualises and clarifies its significance in Jung's life and works. Placing the alchemical Mercurius as a central concern reveals a Jungian interpretation in which the grail legend, alchemy and precessional astrology, as three thematic threads, converge. In such a treatment, Jung's belief in the dawning of a new platonic month emerges as a central consideration and an esoteric perspective on Jung's life and works is brought more fully to light, constructing a life-myth interpretation. The book is comprised of three parts: * Aurea Catena: locating the figure of the alchemical Mercurius within the Western esoteric tradition * Daimonic Encounter: the relevance of this figure in Jung's personal life * Magnum Opus: Jung's portrayal of this figure in key texts such as Synchronicity, Aion, Mysterium Coniunctionis; and Emma Jung and von Franz's The Grail Legend. The Alchemical Mercurius is a unique contribution to analytical psychology, substantially revealing 'esoteric Jung' and providing valuable perspectives on the theme of his myth for our times. The book will appeal to researchers and academics in the field of analytical psychology as well as postgraduate students.