Background/Objectives: The cranial base, especially the posterior cranial fossa, has openings with population-specific morphometry. This study aimed to assess the morphometric characteristics of the major posterior cranial fossa openings (foramen magnum, jugular foramen, internal acoustic opening) in the Turkish population and evaluate their utility for sex estimation. It also aimed to provide population-specific reference values for forensic anthropology and cranial base surgery. Methods: This prospective study included 304 adult skulls (151 female, 153 male) obtained from forensic autopsy cases, all of which had preserved anatomical integrity. Structures in the posterior cranial fossa were exposed following a standardized dissection protocol. A total of 18 morphometric parameters were measured using a digital caliper. Inter-sex comparisons were performed, and the diagnostic performance of the parameters for sex differentiation was evaluated using receiver operating characteristic (ROC) curve analysis. Results: All morphometric parameters and inter-foraminal distances were significantly larger in male individuals compared to females (p < 0.001). Similarly, ellipticity indices were higher in males than in females (all p < 0.001). ROC analysis revealed that right internal acoustic opening transverse diameter (RIAO-T), left and right jugular foramen transverse diameters (RJF-T and LJF-T) parameters possess exceptionally high discriminatory power, yielding accuracies greater than 99%. Conclusions: Components of the posterior cranial fossa exhibit marked sexual dimorphism in the Turkish population. These morphometric data provide valuable anatomical references for forensic identification, aid in preserving neurovascular structures, and support safe surgical planning in cranial base procedures.