The phenomenon of “lone wolf ” terrorism, which has increasingly attracted the attention of scholars, consists of terror attacks perpetrated without the operational involvement of terrorist organizations in initiating, planning, or executing the attack. This phenomenon lacks a clear center of gravity directing the actions of “lone wolf ” terrorists; and as such, it is crucial to understand the system of motivations influencing independent assailants to perpetrate attacks. This article is based on extensive studies conducted on the motivations of “lone wolf ” terrorists by the International Institute for Counter-Terrorism (ICT) at the Interdisciplinary Center (IDC), Herzliya. It seeks to contribute to the literature on the topic by proposing a new model. The “Bathtub Model” suggests that the process of the formation of the “lone wolf’s” decision to perpetrate an attack can be akin to a container of water (such as a bath), which would be filled up by various sources of water, each representing groups and subgroups of motivations. The upper threshold of the “bathtub” model represents therefore the maximal level of the “lone wolf’s” ability to contain his motivations, frustrations, and emotions.