This thesis starts from the intuition that it is possible to oppress oneself. On an initial description, self-oppression is a form of agency in which the agent, though exercising self-control, compromises her own choices in doing so. But, as such, self-oppression seems paradoxical and thus impossible: how can an agent be both the oppressor and the oppressed? And how can she compromise her own choices? The headline aim of the thesis is to offer a conceptualisation of self-oppression, thus establishing it as a possible as well as a distinct form of agency. The strategy of the thesis is rather unusual. In the first chapter, drawing on Aristotle’s philosophy of action, I devise the category of hyperkrasia, designed to capture the phenomenon of self-oppression. I propose that, in hyperkrasia, an agent’s practical reason becomes authoritarian. This category is then further developed throughout the thesis, drawing on Augustine, Foucault, and Merleau-Ponty. Augustine’s notion of a corrupted will provides an account of how choice can be compromised without agency being bypassed: the agent with a corrupted will chooses to φ, but cannot but choose φ. Foucault’s notion of domination provides an explanation of how an agent’s will can be corrupted by factors influencing her perception of opportunities. Merleau-Ponty’s phenomenological account of action shows how our perception of opportunities can draw us toward action. Bringing these elements together, I propose that practical reason can influence an agent’s perception of certain opportunities, drawing her so strongly toward them that she cannot but act on them. As such, she makes a choice; but it is compromised, and this by her own practical reason. This resolves the paradox of self-oppression: it is practical reason which becomes the oppressor, and it compromises the agent’s choices by influencing the way she perceives certain opportunities.