This data release contains the boundaries of assessment units, assessment input data, and resulting fact sheet data tables for the assessment of undiscovered oil and gas resources in the Greater Caspian area. The assessment unit is the fundamental unit used in the National and Global Oil and Gas Assessment Project for the assessment of undiscovered oil and gas resources. The assessment unit is defined within the context of the higher-level total petroleum system. The assessment unit is shown herein as a geographic boundary interpreted, defined, and mapped by the geologist responsible for the province and incorporates a set of known or postulated oil and (or) gas accumulations sharing similar geologic, geographic, and temporal properties within the total petroleum system, such as source rock, timing, migration pathways, trapping mechanism, and hydrocarbon type. The assessment unit boundary is defined geologically as the limits of the geologic elements that define the assessment unit, such as limits of reservoir rock, geologic structures, source rock, and seal lithologies. Machine-readable tables are provided that contain the input and results for each assessment unit summarized in the U.S. Geological Survey (USGS) Fact Sheet. Methodology of assessments are documented in USGS Data Series 547 for continuous assessments (https://pubs.usgs.gov/ds/547) and USGS DDS69-D, Chapter 21 for conventional assessments (https://pubs.usgs.gov/dds/dds-069/dds-069-d/REPORTS/69_D_CH_21.pdf). See supplemental information for a detailed list of files included this data release.