Is Truong a first name or a last name?

Truong is both: a family name in some places and a given name in others. It is mostly a family name in France and the United States.

How to address someone called Truong

Vietnam. Truong is used both ways: 76% of people from Vietnam with this name in our data carry it as a family name. Look at where it sits in the name and how the person signs.
France. Truong is a family name, usually written last. Write Dear Mr. Truong or Dear Ms. Truong.
United States. Truong is a family name, usually written last. Write Dear Mr. Truong or Dear Ms. Truong.

Not sure which part of a full name is which? Check the full name with the country where the person is based.

People recorded in Wikidata who carry Truong as a family name or as a given name, by country of citizenship (78 in total).

Country	As family name	As given name	Family name share
Vietnam	37	12	76%
France	12	0	100%
United States	10	0	100%

Wikidata covers notable people, so counts show how the name is used, not how many people carry it.

As a surname: about 38,267 people in the 2010 census, rank 903 among US surnames.
As a first name: 237 babies born between 1950 and 2017.

More on this naming tradition: How Vietnamese names work.