Renewed interest in Mesozoic exploration, onshore and offshore, in the Gulf of Mexico (GOM) has precipitated a new look at Mesozoic biostratigraphy and how these age-diagnostic bioevents can help to establish a sequence-stratigraphic framework for the basin. We have developed a new chronostratigraphic framework, primarily founded on biostratigraphic age-diagnostic data, specifically developed for Mesozoic strata of the GOM basin. Our goal was to provide a systematic and consistent framework that serves as a reference for the order and timing of depositional sequences and key surfaces in the GOM Mesozoic stratigraphic section. The new chronostratigraphic framework was based on (1) our work delineating significant physical stratigraphic surfaces from seismic and well-log data in the GOM, (2) Mesozoic biostratigraphic data from 202 onshore and offshore wells in the GOM, and (3) published literature from the GOM and other studies. The chronostratigraphic framework was formalized in an online Mesozoic biostratigraphy table and summarized in a Mesozoic stratigraphy chart. The use of the framework was key to our ability to correlate within the GOM basin, and we evaluated several examples of seismic and well-log interpretation using the new chronostratigraphic framework, including onshore-offshore correlation, identification and correlation of source rocks, and interpretation of structural anomalies. These examples illustrated how the chronostratigraphic framework enabled us to reduce uncertainty in identifying and correlating Mesozoic units from land to the deepwater GOM basin. The framework also allowed us to better compare our work with other research groups, within academia and industry, and permitted a higher level of integration of work and comments from various applied industry workers.