Biomarkers are measures of biological processes that reflect normal physiology, disease related changes, or the results of interventions. Biomarkers include blood tests, tests of cerebrospinal fluid obtained by lumbar puncture, brain scanning, and digital information collected from devices such as Fitbit. Biomarkers have become fully integrated into the drug development process and advancing new therapies depends on the availability of information on biomarker-based diagnosis, monitoring, determination of the impact of treatment on the disease, and assessment of the safety of the intervention. There is currently no database that serves as a source of comprehensive and use-specific data of biomarkers. We propose the development of a Biomarker Observatory (BMO) that will systematically capture information on biomarkers and make it available to drug developers and other stakeholders in the drug development process. We will base the BMO in part on our experience with our successful Clinical Trial Observatory.  We propose that the BMO be built, governed, and utilized in partnership with the ADDF.