The main purpose of this special issue of Homicide Studies is to explore the similarities and differences between traditional homicide and a variety of less common homicide forms involving political and other ideological motivations. Scholarly terrorism research has historically manifested most frequently as the psychological study of radicalization processes (Horgan, 2005; Kruglanski et al., 2014) and terrorist group dynamics by political scientists (Abrahms, 2012; Schmid & Jongman, 1988). Conversely, although there are important exceptions (e.g., Hamm, 1993; Smith, 1994), most criminological research on terrorism and violent extremism has been conducted more recently, increasing after the coordinated terrorist attacks of September 11, 2001. The dearth of criminological attention to terrorism in the past, particularly by homicide researchers, is an important gap for several reasons.