Cognomen Willain (Willain 
) , across the world, is a rare surname. The cognomen Willain is habitual in Belgium, where it is quite a rare surname, Estonia, where it is a rare surname, and France, where it is a very rare surname. In absolute terms, it is the most numerous in Belgium, France, and Brazil. Very seldom, Willain is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Willain | Belgium, Myanmar, Brazil, France, Venezuela |