Three-dimensional (3D) reservoir modelling and basin analysis were performed for the Siwa Basin in the North-Western Desert of Egypt. An integrative study from the available data were done, including geochemical data to construct a 1D basin model, petrophysical data to realize the characteristics of the reservoir, and geological data to understand the subsurface geologic setting, has been undertaken. Basin modelling was done for the Siwa A1-X well to determine the burial and thermal history, sedimentation rate, level of maturity, and finally the event chart for the petroleum system. Siwa Basin comprises one petroleum system. The source rock is represented by the Palaeozoic Dhiffah, Desouky, and Zeitoun formations, with fair to good organic richness, producing oil and gas, which entered the oil window in 143.91, 162.87, and 167.31 Ma, and entered the wet gas in 138.75, 141.82, and 143.63 Ma, with sedimentation rate varying from low to high 543.96, 22.79, and 1,404.46 m/Ma, respectively. The Safa Member (Khatatba Formation) is the main reservoir, with hydrocarbon saturation reaching up to 80%, and with a low subsidence rate of 76.43 m/Ma. The Original Oil In Place for the new prospects is 197.177 Stock Tank Barrel (STB), while for the oil reserve is 50.618 Stock Tank Barrel (STB).