The present thesis aims to expand and acquire new knowledge on the emergence of portrait mummies during the Roman period in Egypt and their socio-religious status. The emergence and decorative program of these mummies are commonly understood as an artistic expression of Hellenistic Greek and Roman settlers in Egypt. This attestation is often based upon uncontextualized isolated portraits. The study of uncontextualized isolated portraits has also caused an unsatisfactory approach to dating criteria. In response, the present thesis aims to study contextualized portrait mummies – with the image of the deceased still forming part of the mummy and ideally with an attested find spot – in light of a multicultural society consisting of Egyptian, Hellenistic and Roman cultural and religious traditions.  A total of 85 portrait mummies have been collected to provide context for the expressed cultural traditions. Seven group burials have been reconstructed based upon excavation reports for further contextualization. The results of the collected portrait mummies and reconstructed group burials are subsequently studied against a background of Egyptian, Hellenistic and Roman cultural and religious traditions to highlight dominant cultural features. The results of the present thesis illustrate portrait mummies were an expression of a culturally complex society. The treatment of the body and decorative program suggests cultural and religious notions were rooted within Egyptian traditions that were appropriated, re-defined and adapted by a society comprised of Egyptians, Hellenes and Romans. Portrait mummies consequently express multiple cultural layers. Previously established dating criteria were found to remain to be the most valid and reliable. Contextualized portrait mummies, however, have put forward a new dating criterion that ought to be taken into consideration: octagonal framing.