Olsza was formerly part of the German Empire. In the German Empire, the place was called Olscha.
The place is now called Olsza and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Olscha | German Empire | Mogilno | before the Versailles Treaty |
| Olsza | Poland | Mogilno | after the Versailles Treaty |
| Olscha | German Empire | Mogilno | 1939 |
| Olsza | Poland | Mogilno | 1945 |
| Olsza | Poland | Bydgoszcz | 1992 |