Surname Gustain (Gustain 
) , worldwide, is a very rare cognomen. The family name Gustain is characteristic of Germany, where it is a very rare surname, Canada, and the United States, where it is an extremely rare surname. More prevalently, Gustain is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Gustain | Canada, United States, Germany, Democratic Republic of the Congo, India |