Which royal family member is known as the Duke of Cornwall?

The Duke of Cornwall is a title historically given to the eldest son of the reigning monarch in the United Kingdom. At the time when this question is relevant, Prince Charles held this title as the eldest son of Queen Elizabeth II. The title entails certain responsibilities and privileges associated with the Duchy of Cornwall, which includes managing a significant estate and overseeing various charitable activities.

Understanding the context is essential—this title does not refer to just any member of the royal family but specifically to the male heir apparent. Other members of the royal family, such as Prince William and Prince Harry, do not hold this specific title at the time in question, and The Queen herself does not bear the title of Duke of Cornwall as it is inherently linked to the immediate heir. Thus, Prince Charles stands out as the correct answer due to his direct line as the eldest son of the reigning monarch.