Online Mendelian Inheritance in Man (OMIM®), currently in its 55th year, is a foundational resource in human genetics and genomics. OMIM's goal is to expand the understanding of human biology and disease by providing a timely, authoritative, easily accessible, and computable knowledgebase of the increasingly complex and nuanced relationships between human genes and genetic disorders and traits. OMIM serves diverse scientific communities, including clinical geneticists, health care providers, basic, model organism, translational and clinical researchers and bioinformaticians as well as educators and students in these fields. OMIM.org is accessed by over 25,000 unique daily users worldwide. OMIM's core mission is the naming and classification of Mendelian phenotypes (traits and diseases) and the relationship of the phenotypes to the genes that cause them. This is accomplished by expert review, evaluation, and summary of the peer-reviewed biomedical literature by an expert staff of biocurators and MD and PhD science writers who have decades of experience in synthesizing and incorporating substantive information into rich, structured gene and phenotype entries, comprehensive clinical synopses, and a GeneMap/Morbid Map from which Phenotypic Series are created. As of 31 December 2020, OMIM includes over 25,692 entries, 7,754 clinical synopses, and 489 Phenotypic Series. MIM numbers are internationally recognized as unique identifiers of Mendelian disorders and appear throughout the biomedical literature. OMIM entries and clinical synopses are mapped to controlled-vocabulary resources such as ICD10, SNOMED, HPO, and the UMLS. These mappings are searchable and available through the API to facilitate computational survey and data mining, as well as the functional integration of OMIM data to enhance analysis pipelines, dissemination, and computability. In addition, OMIM leverages data from a variety of other resources to augment its unique content and collaborates with other informatics resources and curation efforts such as ClinVar, ClinGen, and the Monarch Initiative to harmonize data content. To broaden and improve OMIM as the preeminent resource for the clinical, academic, and commercial research community, we have expanded our current coverage by adding expert scientific and bioinformatics staff and will continue to enhance its structural compatibility with other entities, maintain industry best practices in database and software development, and provide Web Services and REST API in a targeted and cost- effective way. We will augment efficient and automated processes to mine the biomedical literature in the curation process and introduce new data visualizations and search functions. To further optimize the end-user experience, we have experienced user support staff to provide technical assistance and training. We regularly solicit feedback and community input to improve the functional features and free accessibility of our resource. OMIM is an essential resource for clinical medicine, model organism research, and disease gene and therapeutic discovery.

Now in its 55th year, Online Mendelian Inheritance in Man (OMIM) is a foundational resource, a knowledgebase of human genes and genetic disorders and traits that is accessed annually by over 2.7 million unique users worldwide. Its core mission is (1) describing, naming, and classifying genetic diseases, and (2) providing easily accessible and computable information on gene-disease relationships through rich, structured text, brief clinical synopses, and a table that tracks the progress of disease-gene discovery. Expert MD- and PhD- biocurators review and summarize information from the biomedical literature to create this authoritative, comprehensive and timely resource that is essential for the practice of medicine, and directly advances basic, translational, and clinical research, as well as therapeutic discovery.