American female psychologists who contributed to the development of industrial and organizational (I/O) psychology during the early years are presented. An overview of the education, scholarship, practice, and professional service activities is provided for 4 pioneers (Marion Almira Bills, Elsie Oschrin Bregman, Lillian Moller Gilbreth, and Mary Holmes Stevens Hayes). These early female I/O psychologists blended research, applications of psychology, and service in ways that prefigure current science and practice within the field. Incorporating women into the history of I/O psychology is imperative to the attainment of a more complete understanding of the past and a fuller comprehension of the present. In addition, lessons for current and future I/O psychologists are ascertained from the accomplishments of these pioneers.However carefully the present is studied and however refined the techniques of analysis, the present is not fully comprehended if the past is ignored or distorted. (Gutman, 1977, p. 259) This article presents female psychologists who contributed through scholarship, practice, and service to the discipline of industrial psychology (now known as industrial and organizational [I/O] psychology) during its developmental years . Changes in society, generally, and in psychology, particularly, combined with opportunistic approaches and individual characteristics (e.g., intelligence, assertiveness, perserverance) empowered these individuals to research and practice I/O psychology. Their accomplishments illustrate the modern idea of the scientist-practitioner model; they used scientifically rigorous methods to conduct research in applied settings and upheld scientific integrity when implementing the results of