In the 1980s, a coalition of individuals who hoped to make ethical non-monogamy a socially acceptable lifestyle created the contemporary polyamory movement. Many of those who made up this movement were ex-hippies who had deep connections to the communal and free love movements of the 1960s. Although they were initially ridiculed in the public sphere, during the past 20 years polyamory has become an increasingly accepted cultural phenomenon. This dissertation examines the intellectual and cultural foundations of the polyamory movement from the 1920s until its birth in the 1980s. It then traces the movement’s inception, before detailing how its ideas became culturally influential by the second decade of the 21^stcentury.