Cognomen Thelby (Thelby 
) , all around the world, is an extremely rare family name. The surname Thelby is habitual in Latin America and the Caribbean, particularly Colombia, where it is a very rare surname. Also, Thelby is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Thelby | Philippines, Colombia, United States, South Africa |