Who was the last monarch of Britain to rule over the colonies?

The last monarch of Britain to rule over the American colonies was King George III. He reigned during a significant part of the period leading up to the American Revolution, which included the years when the colonies were seeking independence from British rule. His policies and the taxation measures imposed on the colonies contributed to growing discontent, ultimately culminating in the colonies declaring independence in 1776.

Although Queen Victoria, King Henry VIII, and King Edward VII are notable figures in British history, their reigns occurred either after the American colonies had declared independence or in periods that were not directly linked to the governance of the colonies. Therefore, King George III stands out as the monarch directly associated with the colonial governance just before the loss of the American territories, making him the correct answer.