IntroductionThis chapter discusses the recent literature 1 on open non-monogamies, or non-monogamous arrangements that are known about by, at the very least, all the involved intimate partners. (This specifically excludes a consideration of the growing parallel literature on secret non-monogamies (e.g. infidelity, adultery, and cheating) addressed in relation to monogamy and marriage in Ziegler, Conley, Moors, Matsick, & Rubin, Monogamy, this volume.)This growing field comprises work on polyamory (discursively ethical or consensual non-monogamy); on polygamy (plural marriage, usually -but not exclusively -polygynous: Muslim, Christian, and other); on swinging (sometimes known as The Lifestyle, a subculture devoted to casual open sex); and on non-monogamies outside these three major formulations. This last category includes open marriages and relationships; alternative marital arrangements, sometimes referred to as swapping 2 or co-marital sex; friends with benefits; group sex (e.g. threesomes, orgies); open-sex commune experiments (e.g. the Oneida intentional community); and otherwise-unnamed non-monogamous intimate practices such as those that can occur in some lesbian, gay, bisexual, and kink subcultures. Finally, it also includes work that considers nonmonogamies broadly across these categories. These practices have different histories, etymologies, facets, and politics. Some of these practices are thousands of years old, some are merely decades old and some are just being fleshed out; some have their origins in religion or spirituality, others in a staunch and iconoclastic secularism. Taken together, however, they form a present and undeniable facet of contemporary intimacy that has been growing in prominence and significance in the public sphere and public culture since at least the early 1990s (Rambukkana, 2015). Engaging with open non-monogamies is no longer something relegated to societal margins in the life of Western societies; it has shifted to be a part of the centre -albeit a part that sits somewhat uneasily 236