Equestrian sports are unavoidably interspecies and undeniably dangerous. Whilst there has been qualitative research into the human–horse relationship, and quantitative research into horse riding, injury and risk, there remains a need to understand how risk perception and experience is subjectively implicated in, through and by the human–horse relationship, and vice versa. Doing so requires reconciling animal studies with risk theory. As a high-risk interspecies sport, eventing provides an exemplar case study for critiquing, extending and reconciling posthumanism and risk theorisation. This paper draws from interviews with 21 participants of the high-risk equestrian sport of eventing to explore the mutual benefits of using ‘risk’ as a point d’entrée for analysing human–horse relations. Findings were largely consistent with three popular theories of voluntary risk-taking: edgework, flow and sensation-seeking. However, the involvement of an animal – the horse – stimulates a critical reconsideration of internal/external ‘control’; identifies a role for flow as risk mitigation/safety; and suggests that edge workers in high-risk interspecies sports do not just confront edges – they cross them. This paper thus distinguishes interspecies sports as a distinct and productive field of interdisciplinary research. It proposes further mixed-methods research that is required to more fully evaluate the usefulness of existing risk theory for understanding participant experiences of high-risk interspecies sports.