While significant efforts have been made by organizations and governments to promote sustainable tourism practices, it is evident that a shared framework for designing, monitoring, and planning tourism strategies is still lacking. This study aims to address the challenges of information sharing, comparability of approaches, and dissemination of lessons learned across the tourism ecosystem. Insights from many disciplines, including tourism, ecology, economics, and urban planning, are used to suggest the adoption of a methodological perspective grounded in complex systems theory. The study’s theoretical and analytical framework aims to provide a comprehensive understanding of the spatial complexity involved in defining and managing tourist systems at the territorial scale. By integrating insights from big data, local systems, and specialized tourism, the research offers a nuanced and holistic approach to long-range planning for territorial development. After a thorough examination of the existing literature and research, critical aspects related to tourism strategy planning have been identified. These include challenges in taxonomy, definitions of sustainability in tourism development, and the absence of tools for assessing and monitoring tourism ecosystem components at a territorial scale. The methodology consists of two interconnected phases. In the first phase, a clear taxonomy is adopted, which is derived from an extensive literature review. This taxonomy specifically targets the identified limitations in existing frameworks. It comprises three main ontological classes: ‘Destination Area’ (DA), ‘Tourism System’ (TS), and ‘Tourism Ecosystem’ (TE). These classes serve as analytical scales and offer both spatial and functional interpretations. Emphasizing sustainability as a focal point, this approach stands as a crucial tool for supporting territorial planning. The research outcomes contribute not only to the academic understanding of territorial-scale tourism but also provide practical insights for decision-making and planning processes. This study proposes a comprehensive framework for analyzing and planning tourism ecosystems, with the aim of promoting sustainable development in the wider territorial landscape.