<p>This study provides a multiproxy detailed analysis of the Eocene–Oligocene sedimentary succession exposed in northern Bahariya Depression (Western Desert, Egypt), integrating sedimentology, paleontology, and litho- and biofacies investigations. The Eocene rocks described in this area constitute, from base to top, the Naqb (early Eocene), Qazzun and El-Hamra formations (middle–late Eocene), which are unconformably overlain by the Oligocene rocks of the Radwan and El-Ris formations, respectively. Four benthic foraminiferal and five macrofuanal assemblages were identified from the Eocene succession and interpreted in terms of palaeoecology and palaeobiogeographic distributions. Field-based description supported by detailed petrographic investigations of the Eocene rocks enabled the discrimination of sixteen microfacies types that form four distinctive genetically-related facies associations deposited primarily in marginal-marine neritic, tide-dominated environments. These environments correspond, respectively, to peritidal flat, lagoonal–restricted bays, shoal and platform margin reefal environments positioned on a gently dipping homoclinal inner to proximal mid-ramp setting. The vertical transitions of these facies associations, demonstrating facies changes over time, signify oscillations of the regional/eustatic sea level. Facies analysis of the Oligocene rocks showed predominant massive and cross-bedded sandstone, typically of quartz-arenite, deposited by sinuous, meandering-style fluvial streams. The upper Oligocene–Miocene strata consist of a well-developed profile of calcretes and dolocretes accumulated in an alkaline–Mg²⁺ enriched shallow lacustrine depositional system under evaporitic conditions. Vertical facies change from a transgressive to a regressive systems tract was developed essentially in response to regional/global eustatic sea-level fluctuations, which were linked mainly to the climatic shifts from the Eocene greenhouse to the Oligocene icehouse, in addition to the non-negligible influence of the regional tectonics. The identified fossil assemblages exhibit a dominant Tethyan affinity, corresponding to those of the Arabian, northern African, Iranian-Indian, and southern Europe carbonate platforms. This study thereby adds invaluable information about facies and sequence architectures, and palaeobiogeographic distribution of the Tethyan shallow marine carbonate platforms formed during the Paleogene.</p>