This article is the first of a two part review of the psychoanalytic theory of depression. In this first part of the review the work of the major contributors to the psychoanalytic theory of depression is discussed. The writings of Abraham, Freud, Rado, Klein, Jacobson, Benedek, Bibring, Spitz, Sandler and Bowlby, among other, are presented and critically reviewed by the author. The work of these authors has been selected for this review because they have made the most seminal contributions to the development of the psychoanalytic theory of depression. Necessarily those authors whose contributions have been largely clinical have not been included, the major focus of this review being theoretical. In reviewing the writings of the major contributions the major themes in the theory of depression can be discussed. These themes will form the subject of the next paper in this review.