The Alaska Geochemical Database Version 4.0 (AGDB4) contains geochemical data compilations in which each geologic material sample has one best value determination for each analyzed species, greatly improving efficiency of use. The relational database includes historical geochemical data archived in the USGS National Geochemical Database (NGDB), the Atomic Energy Commission National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance databases, and the Alaska Division of Geological and Geophysical Surveys (DGGS) Geochemistry database. Data from the U.S. Bureau of Mines and the U.S. Bureau of Land Management are included as well. The data tables describe historical and new quantitative and qualitative geochemical analyses. The analytical results were determined by 120 laboratory and field analytical methods performed on 416,333 rock, sediment, soil, mineral, heavy-mineral concentrate, and oxalic acid leachate samples. The samples were collected as part of various agency programs and projects from 1938 through 2021. Most samples were collected by agency personnel and analyzed in agency laboratories or under contracts in commercial analytical laboratories. Mineralogical data from 18,138 nonmagnetic heavy-mineral concentrate samples are also included in this database. The data in the AGDB4 supersede data in the AGDB, AGDB2, and AGDB3 databases but the background about the data in these earlier versions is needed to understand what has been done to amend, clean up, correct, and format these data. Data that were not included in previous versions because they predate the earliest agency geochemical databases or were excluded for programmatic reasons are included here in the AGDB4. The AGDB4 data are the most accurate and complete to date and should be useful for a wide variety of geochemical studies. They are provided as a Microsoft Access database, as comma-separated values (CSV), and as an Esri geodatabase consisting of point feature classes and related tables.