Surname Siarhiej (Сергей 
, Сяргей , Siarhiej 
) , around the world, is a widespread last name. The cognomen Siarhiej is characteristic of Armenia, where it is a common surname, Kyrgyzstan, and Moldova (explore the name in all countries). Not in comparison with a country's population, it is commonest in Russia, Kyrgyzstan, and Belarus. Much more frequently, Siarhiej is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Сергей | Kazakhstan, Ukraine, Belarus, Russia, Azerbaijan |
| Сяргей | Belarus |
| Siarhiej | Poland, Belarus |
Serge, Sergei, Sergej, Sergejs, Sergejus, Sergey, Serghei, Sergi, Sergio, Sergios, Sergiu, Sergius, Sergiusz, Serguei, Sergueï, Serguéi, Serhij, Serxio, Siarhei, Siarhej, Siergiej, Syarhey, Szergej, Sérgio, Σέργιος, Сергий, Сергиос, Сергиус, Сергиуш, Сергій, Серджо, Серджу, Серж, Сержи, Сержио, Сержиу, Серхи, Серхио, Серый, Серёга, סרג'י, סרגיוס, סרגיי, سرجيوس, سيارى, سيرج, سيرجى, سيرجي, سيرجيو, سيرغي, セルゲイ, セルジョ, and セルヒオ