Surname Thoennessen (Thoennessen 
) , throughout the world, is a rare family name. The last name Thoennessen is habitual in Austria, where it is a rare surname, Germany, and the United States, where it is an extremely rare surname.
| VARIANT | COUNTRY |
|---|---|
| Thoennessen | Germany, Austria, Spain, United States |
Thoenneßen, Thönnessen, and Thönneßen