As part of a broader spectrum of collaborative activities underpinning nuclear materials research, the Nuclear Energy Agency is supporting worldwide efforts towards the development of advanced materials, including fuels for partitioning and transmutation purposes and accident-tolerant fuels (ATFs). This state-of-the-art report on ATFs results from the collective work of experts from 35 institutions in 14 NEA member countries, alongside invited technical experts from the People’s Republic of China. It represents a shared and consensual position, based on expert judgment, concerning the scientific and technological knowledge related to ATFs. The report reviews available information on the most promising fuels and cladding concepts in terms of properties, experimental data and modelling results, as well as ongoing research and development activities. It also includes a description of illustrative accident scenarios that may be adopted to assess the potential performance enhancement of ATFs relative to the current standard fuel systems in accident conditions, a definition of the technology readiness levels applicable to ATFs, a survey of available modelling and simulation tools (fuel performance and severe accident analysis codes), and the experimental facilities available to support the development of ATF concepts. The information included in this report will be useful for national programmes and industrial stakeholders as an input to setting priorities, and helping them to choose the most appropriate technology based on their specific strategy, business case and deployment schedules.