Family name Eustacius (Eustacius 
) , across the world, is an extremely rare cognomen. Predominantly, Eustacius is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Eustacius | United States, Brazil |
Efstathios, Eustac, Eustacchio, Eustace, Eustach, Eustache, Eustachio, Eustachy, Eustacio, 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