Informal caregivers are people who provide (unpaid) assistance to a parent or relative because they cannot perform certain tasks themselves. Informal caregiving has been shown to be a rewarding role in many ways, but it also carries with it the potential for negative consequences. The understanding of these consequences has been studied primarily through the concept of the "burden" of being an informal caregiver, but this area of research suffers from several limitations, including conceptual and empirical heterogeneity. This work therefore proposes to adapt the concept of burnout to the context of informal care, in order to better understand how these deleterious consequences can occur. This adaptation is achieved through a qualitative and quantitative synthesis of existing evidence, but also through theoretical and empirical research. As a result, this work highlights that informal caregivers are at risk of experiencing some form of burnout and proposes a new framework for addressing the issue of informal caregiver burnout itself. Based on this framework, empirical investigations support its relevance, while contributing to a better understanding of this phenomenon. Based on these findings, several refinements to this model and key issues in the adaptation of burnout to informal care are discussed. Overall, this work provides new insights into the field of informal caregiver burnout research and a new framework for studying its determinants and consequences. In doing so, it aims at better understanding how informal care can take a deleterious turn, but also to provide keys to intervene when necessary.