This chapter provides an overview of left-wing terrorism in the United States, with a focus on key groups, patterns over time, primary targets, and the main tactics utilized by the movement. This overview starts with the traditional groups of the 1960s, whom were based on anti-Imperialist and anti-Capitalist philosophies. It then covers the development of radical environmental and animal rights groups from the 1980s and finishes with a discussion of the future of the ideology, which includes elements from both traditional groups and this more recent “single-issue” iteration.