Across the world, Sebastian Guillermo (Sebastian Guillermo 
) is a rare masculine forename. The first name Sebastian Guillermo is characteristic of Latin America and the Caribbean, particularly Chile, where it is quite a rare male name, Peru, where it is a very rare male name, and Argentina. Very seldom, Sebastian Guillermo is the last name as well as the forename.
| VARIANT | COUNTRY |
|---|---|
| Sebastian Guillermo | Spain, Argentina, Peru, Ecuador, Chile |