Many historians have looked at the power exercised by Mary and Elizabeth with links to, or separate works on, Mary’s accession and her marriage to Philip or Elizabeth’s reign as a single queen; the relationship between her gender and power and her many courtships and marriage pressures. The research conducted for this study differs from previous studies as it will comparatively evaluate whether it was more effective to be a single or married queen regnant regarding the exercise of power and authority and whether a queen regnant’s power would be diminished, maintained or increased through their marital status. It will examine how Mary’s exercise of power and authority changed between being a single or married queen regnant as well as assessing Elizabeth’s power and authority throughout her reign as a single queen and how it directly related to her marital status; comparing the two queen’s reigns and marital statuses in relation to their power. This study will also build upon the historiography by using examples, where necessary, of other early modern European regnant queens to emphasise the argument that marital status did indeed have a significant effect on the power and authority of a regnant queen.