At its inception as a specialty within psychology in the first decades of the 20th century, the history of psychology was usually conceived as an extension of the history of philosophy, with perhaps some special attention given to the development of modern science. Within the last thirty years, the history of psychology has come of age and has become as diverse as its sprawling subject: historical studies have proliferated as psychologists’ activities have expanded and diversified. Alongside the original purpose of delineating the evolution of psychology from the historical roots of science, philosophy, medicine, and other intellectual traditions, recent histories of psychology have been very concerned with describing and explaining the social, organizational, and political context of psychological events and theories. Thus, the scholar of the history of any area of psychology would do well to become acquainted with other specialized literature not only of the specific area of psychology in which the historical events take place, but also of the political, social, and economic systems which condition them. Those with an interest in the history of any area of psychology which is not represented in any part of this necessarily selective article should adopt the attitude of confident pioneering which characterizes the leading historical scholarship in psychology today, school themselves in some basic techniques of historical investigation, and contribute to the further deepening and elaboration of our rich historical record. The timeframe of this article is the period from 1900 onward, mainly in the United States and Western Europe. This article contains a brief orientation and a section on the history of psychology as represented in Textbooks, classic and modern. There are also several sections expanding on the range of essential reference resources: Encyclopedias, Dictionaries, and Bibliographies; Compendia and Readers, along with collections of primary-source excerpts; Journals and blogs; Illustrations, Artifacts, and Archives; Timelines and Rankings of Eminence; Biography and Autobiography; and background about major Professional Organizations connected to the history of psychology. The philosophical context is represented by sections containing critiques of standard textbook history, sections that contextualize psychology’s history within the philosophy of science (see History and Philosophy of Science), a section on disciplinary taxonomy organized around the question of the Unity vs. Diversity of Psychology, and a section on several “crises” in 20th-century psychology. There is a selection of works surveying the transformation of psychology from science to applied technology (see the Transition from Science to Technology, 1880–1970). Histories of Subfields—theoretical and applied, with a special section on clinical psychology—are included, along with sections detailing the history of psychology in the contexts of Race, Ethnicity, and Culture as well as Gender. Finally, the section on Future Directions includes a selection of works pointing toward areas of potential future development in the field.