Targeting a productive and rewarding fit between the worker and the work setting, industrial-organizational (I-O) psychology is heavily vested in identifying situational factors as main effects on work behavior, as moderators of personological (e.g., personality) influences, and as outcomes in understanding the workplace as a dynamic and evolving system. Here, we focus on the role of situations in the I-O psychology practices of job analysis, personnel selection and validation, training, work motivation, leadership, job design, and organizational development. Then, select workplace situational taxonomies are presented from the literature, organized by task (e.g., RIASEC), group (team task type), and organizational (e.g., culture) levels. Several broad situational features (e.g., situational strength, situational trait-relevance) are also identified. The chapter closes with some general observations aimed at advancing integration of situational factors in the psychology of work.