Around the world, Eustac (Eustac 
) is an extremely rare male first name. Much less frequently, Eustac is the last name as well as the forename.
| VARIANT | COUNTRY |
|---|---|
| Eustac | United States |
Efstathios, Eustacchio, Eustace, Eustach, Eustache, Eustachio, Eustachy, Eustacio, Eustacius, Eustacjusz, Eustahije, Eustaqui, Eustaquio, Eustasio, Eustasius, Eustathios, Eustazio, Eustazy, Eustațiu, Eustácio, Eustáquio, Evstafy, Evstahij, Ostap, Stathis, Ευστάθιος, Στάθης, Астафий, Евстатий, Евстафий, Евстахий, Остап, Остафий, Стафей, Эсташ, Юстас, and Євстафій