Søst was formerly part of the German Empire. In the German Empire, the place was called Sös.
The place is now called Søst and belongs to Denmark.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Sös | German Empire | Apenrade | before the Versailles Treaty |
| Søst | Denmark | Aabenraa | after the Versailles Treaty |
| Søst | Denmark | Sønderjylland | 1993 |