Cognomen Сеи (Sei 
, Sey 
, Сеи 
) , in all the world, is a common last name. The last name Сеи is habitual in Gambia, where it is a common surname, Ghana, where it is quite a common surname, and Malaysia, where it is quite a rare surname. In absolute terms, this name is the most popular in Ghana, India, and Malaysia. Likewise, Сеи is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Sei | Japan, Malaysia, Ghana, India, Myanmar |
| Sey | Gambia, Malaysia, Ghana, India, Myanmar |
| Сеи | Russia |