The Late Jurassic to Early Cretaceous strata of the Eastern Gulf of Mexico (EGoM) are one of the world's major hydrocarbon reserves. However, there is a lack of published palynology studies from these strata. This research aimed to fill that data gap by producing a biostratigraphy based on dinoflagellate cyst assemblages using data collected from three wells around the EGoM: VK117, DC353 and CH265. The Gulf of Mexico is a structurally complex area in terms of its tectonic setting. This unusual depocentre therefore requires a well age-constrained biostratigraphy to be established to enable correlation of strata and structures around the EGoM basin. Rich assemblages of palynomorphs, dominated by dinoflagellate cysts, have been recovered from 175 samples taken from the three wells. These have been analysed using a transmitted light microscope to collect the palynofacies data, as well as systematically describing 164 dinoflagellate cyst species and collate quantitative data concerning their occurrence/abundance. These data were then compared to adjacent locations to produce a working biostratigraphy of the EGoM. Further analysis of the palynodebris and palynomorphs has presented information concerning the depositional environments. These data were interpreted using a Tyson Ternary Kerogen Plot (AOM– phytoclasts–palynomorphs) and compared to a Ternary Liptinite–Vitrinite–Inertinite Kerogen Plot to indicate hydrocarbon source potential of the surrounding rocks. The kerogen associations indicated by the Ternary plots for two wells were then compared to the Palynomorph Darkness Index (PDI). To test the robustness of the PDI calculations and if they can be used as an alternative indicator of thermal maturity using a dinoflagellate cyst (Sentusidinium explanatum) as the palynomorph subject, it was compared with vitrinite reflectance. This development of a robust biostratigraphical model for the EGoM basin will greatly facilitate upcoming exploration and development activities in this basin and ensure future energy security.