ambassador

US /æmˈbæsədɚ, -ˌdɔr/

・

UK /æm'bæsədə(r)/

Official representing a country in another country
A diplomatic agent of the highest rank accredited to a foreign government or sovereign as the resident representative of his or her own government or sovereign or appointed for special and often temporary duty.
A person who acts as a representative or promoter of a specified activity.