This chapter traces a history of British Decadent sexualities as elemental, pre-normative attractions and fulfilments, considering how early sexological discourse encouraged conceptions of Decadent sexuality to arise and then likewise feed into more recent, posthumanist notions of eco-sexuality. But recognizing a non-binary Decadence of dissemination, proliferation and contagion requires one to imagine attractions and repulsions that do not merely decentre the human, but operate with a conceptual core that itself is not built in response to human identity, culture or politics in the first place. One possibility lies in Heinrich Kaan’s theory, articulated in his study Psycopathia Sexualis (1844), that a natural excess of imagination fosters realms of ‘chaos’ in plant and animal (including human) sexualities. Early sexological works such as Kaan’s encourage one to understand non-normative sexuality not as one of various deviations characterizing the Decadent movement, in fact not as a deviation at all, but as a natural phenomenon that preceded and gave shape to the cultural paradigms that Victorians and those who followed came to see as Decadent.