Who is the youngest US ambassador?

The U.S. requires that you be 21 years old before you are given diplomatic accreditation to the country you are serving in.

Retired Foreign Service Officer

But there's a lot of Youngest Ambassadors the first one is Samantha Smith, she was just 13 years old, she was called the Ambassador for Peace and a Peace Activist between US and the Soviet Union in Cold War, unfortunately she was died in a Plane Crash in 1985.