The concept of woman-power existing in the highest circles of society in the Mediterranean world is proven, through a detailed study of the career of Cleopatra I. Cleopatra I, daughter of the Seleucid king, Antiochus III, wife of the Ptolemaic king, Ptolemy V, and mother of the Ptolemaic king, Ptolemy VI, became the first female regent in the Hellenistic period. Her regency was a crucial precedent for her female descendants, who all became joint co-rulers with their husbands and enjoyed much greater powers than any other queens before them. The difficulty of this study was in the lack of sources. Virtually nothing is known about Cleopatra I's career and queenship, which, as a result, required a thorough discussion of not only her predecessors and their precedents, but also her own policies and precedents. The thesis is divided into five chapters and fifteen appendices, the last six appendices serving as a sourcebook. Chapter One describes in detail the immense influence of the Ptolemaic ministers and their oligarchic faction at the court, especially during the reigns of the weaker Ptolemaic kings before Cleopatra I's time, and. However, as influential as these powerful Ptolemaic ministers were, a strong monarch, such as Cleopatra I, was able to suppress their large influence on the monarchy. Having suppressed the influential ministers at the court, Cleopatra I utilised another group of courtiers. These courtiers, eunuchs, came from her own retinue and are the focus of Chapter Two. This chapter documents the introduction and institutionalisation of eunuchs into the Ptolemaic court by Cleopatra I. Much as Cleopatra I's descendants had to rely on her precedents to gain influence and power at the Ptolemaic court, Chapter Three looks at Cleopatra I's three most influential and important predecessors, Arsinoe II, Arsinoe III, and Hatshepsut. These three queens were vital to Cleopatra I’s future success, since each contributed greatly to Cleopatra I’s acceptance and appointment as the first female Ptolemaic regent. The last two chapters of the thesis focus on Cleopatra I. Chapter Four discusses extensively the greater rights and privileges Cleopatra I enjoyed when viewed as the Pharaoh's Wife. However, even with these increased rights, Cleopatra I failed to be recognised and acknowledged any differently than her predecessors had. It is in the last chapter, Chapter Five, that Cleopatra I’s power and influence at the court become manifest. This chapter discusses in what areas of the queenship Cleopatra I, during her regency, established new precedents and how her precedents and policies affected royal women not only in her own Ptolemaic kingdom, but also all over the Mediterranean.