The concept of the ecological niche is fundamental to understanding species distributions but it often overlooks the critical role of demography in shaping said distributions. Conversely, demographic theory has traditionally neglected how vital rates vary across environments, limiting our understanding of population dynamics across species’ ranges. Over 50 years ago, Maguire proposed conceptualising the ecological niche as composed of multiple “demographic niches” corresponding to separate vital rates such as survival, development, and reproduction. Despite its potential for ecological research, Maguire’s perspective never really took off. Here, we introduce the “demographic niche concept” (DNC), a contemporary evolution of Maguire’s perspective, integrating recent advances in niche theory and demography to formalise the DNC. We first outline the theoretical foundations of the DNC, focusing on vital rate variation along environmental gradients and its role in shaping ecological niches. We then formalise the definition of the DNC, explore how demographic niches and their boundaries are determined, and introduce a framework for applying the DNC in environmental and geographic spaces. Importantly, we present the DNC as a tool for conservation planning by improving our ability to identify critical areas where specific demographic processes are vital for species persistence or absent under global change. Throughout this review, we also explore methods for modelling and integrating demographic niches and discuss their relevance for addressing global challenges such as climate change. By integrating the ecological niche with demographic theory, we propose testable hypotheses on how and why vital rates vary within niche space, the current frontier of the DNC. Finally, we identify key knowledge gaps and suggest research directions to address these gaps. By advancing the conceptual and methodological tools of the DNC, this review establishes a foundation for future empirical research and applications, offering new directions for ecological theory and conservation amidst a changing world.