What title did Charles V hold during his reign?

Charles V held the title of Emperor of the Holy Roman Empire during his reign, which was a significant and influential position in Europe during the 16th century. As Emperor, he ruled over a vast and diverse realm that included various territories across Europe, including parts of modern-day Germany, Italy, the Netherlands, and Spain. His reign was marked by challenges such as the Protestant Reformation and conflicts with France, which emphasized the political and religious tensions of the era.

His role as Emperor meant that he wielded considerable power and influence over both secular and ecclesiastical matters within the empire. This title was crucial in shaping the political landscape of Europe at the time, as it allowed him to assert authority over a wide range of territories and influence European politics significantly. The Holy Roman Empire itself was a complex entity, with a decentralized structure that required a monarch who could navigate various interests and alliances.

The other titles listed do not apply to Charles V, as he was neither a King of France nor a King of England, nor did he hold the ecclesiastical position of Archbishop of Canterbury. His focus on the Holy Roman Empire and his role in shaping the Reformation and European politics make the title of Emperor the most accurate designation of his authority.