Nowadays, the circular economy represents a promising strategy for achieving sustainable development through optimising resource efficiency, extending product lifespans, and reducing environmental impacts. Despite the growing interest in circular design practices, companies often face difficulties integrating these principles into their established New Product Development (NPD) processes. This is mainly due to the overwhelming number of available design tools and methods, which are fragmented, challenging to navigate, overlap in functionality, and lack standardisation. This study provides a comprehensive mapping, classification, and analysis of 77 existing circular design tools identified through a systematic literature review and supplementary online searches. The tools were systematically categorised according to format, data type, industry sector, circular strategies, innovation focus, aims, and applicability across the NPD stages. The results indicate a predominance of physical, qualitative, and sector-agnostic tools, emphasising circularity integration within the Discover, Define, and Develop phases of the design process. This structured classification facilitates stakeholder navigation of existing resources, highlighting opportunities for more targeted, industry-specific tool development, consumer-oriented approaches, and the importance of considering Industry 4.0 technologies in circular design practice. Future research could address these gaps by developing customised frameworks, validating tool effectiveness through real industrial applications, and promoting deeper integration of circular design tools within NPD practices and business objectives.