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