The United States National Library of Medicine (NLM), located in Bethesda, Maryland, is recognized as the world's largest medical library, housing an extensive collection of over seven million items, including rare and ancient works. Established in 1836 as the Library of the Surgeon General's Office, it underwent a significant transformation in 1956 when it was officially renamed the National Library of Medicine and moved to its current modern campus in 1962.

NLM is a global leader in making medical and scientific information accessible, notably through its freely available digital resources such as PubMed and MEDLINE, which provide millions of journal article references. Pioneering efforts like the 1986 "Grateful Med" project significantly broadened direct access to its vast databases for health professionals. Beyond these, the NLM also operates the National Center for Biotechnology Information (NCBI) and maintains crucial public health tools like ClinicalTrials.gov and ChemIDplus, alongside specialized programs for toxicology, environmental health, and radiation emergency management. As of December 2025, Stephen Sherry was the acting director, overseeing NLM's continued innovation in health information.