Family name גאיוס (Gaj 
, Gaius 
, Qay 
) , all around the world, is a common surname. The surname גאיוס is habitual in Suriname, where it is quite a rare surname, Poland, and Papua New Guinea. In absolute terms, it most frequently occurs in Nigeria, Poland, and India. Also, גאיוס is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Gaj | Nigeria, United States, Italy, Poland, India |
| Gaius | Nigeria, Democratic Republic of the Congo, Cameroon, Papua New Guinea, India |
| Qay | Pakistan, Germany, Malaysia, Indonesia, United States |
| גאיוס | Israel |