Frustration–aggression theory, more commonly known as the frustration–aggression hypothesis, ranks among the most seminal and prolific theories in research on aggression. From its beginnings in the late 1930s until today, it has been applied and studied in a variety of areas, including clinical and social psychology, ethnology, sociology, criminology, and medical research. While frustration–aggression theory has also been used to explain the behavior of animals (see, e.g., Berkowitz, 1983; Scott, 1948), the present chapter will focus exclusively on applications in the study of human behavior. Given the scope and targeted readership of this handbook and the origin of the theory, the focus will be on the social sciences, specifically psychology. Within the discipline of psychology, frustration–aggression theory has been used in a variety of domains, ranging from self-regulation (Harrison, Genders, Davies, Treasure, & Tchanturia, 2011) and imitation learning (Hanratty, O’Neal, & Sulzer, 1972) to developmental (Jegard & Walters, 1960; Nelson, Gelfand, & Hartmann, 1969), organizational (Fox & Spector, 1999; Spector, 1978), and media psychology (Breuer, Scharkow, & Quandt, 2015; Wingrove & Bond, 1998). There is, overall, ample empirical evidence for the link between frustration and aggression. However, the original theoretical explanation for this relationship has developed and become more refined over the decades, and competing theoretical considerations have emerged.