AIMS: The NatIonal Danish endocarditis stUdieS (NIDUS) registry aims to investigate the mechanisms contributing to the increasing incidence of infective endocarditis (IE) and to discover risk factors associated to the course, treatment and clinical outcomes of the disease. METHODS: The NIDUS registry was created to investigate a nationwide unselected group of patients hospitalized for IE. The National Danish healthcare registries have been queried for validated IE diagnosis codes (International Classification of Disease, 10th edition [ICD-10]: DI33, DI38, and DI398). Subsequently, a team of 28 healthcare professionals, including experts in endocarditis, will systematically review and evaluate all identified patient records using the modified Duke Criteria and the 2015 European Society of Cardiology modified diagnostic criteria. The registry will contain all cases with definite or possible IE found in primary data sources in Denmark between January 1, 2016, and December 31, 2021. We will gather individual patient data, such as clinical, microbiological, and echocardiographic characteristics, treatment regimens, and clinical outcomes. A digital data collection form will be used to the gathering of data. A sample of approximately 4,300 individual patients will be evaluated using primary data sources. CONCLUSIONS AND PERSPECTIVES: The NIDUS registry will be the first comprehensive nationwide IE registry, contributing critical knowledge about the course, treatment, and clinical outcomes of the disease. Additionally, it will significantly aid in identifying areas in which future research is needed.