ambassador · noun C /æmˈbæs.əd.ər/
ambassador
B2 the main official sent by a government of a country to represent it in another country
Dictionary examples:
Britain's ambassador in Moscow has refused to comment.
She's a former ambassador to the United States.
Learner example:
On the first floor [is] the "star'' of the museum: a splendid grand piano built in 1893, which was offered by the Queen to the French ambassador in 1895. (First Certificate in English; B2; French)