Siedlec was formerly part of the German Empire. In the German Empire, the place was called Zelz.
The place is now called Siedlec and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Zelz | German Empire | Sorau (Lausitz) | 1939 |
| Siedlec | Under Polish administration | Żary | 1945 |
| Siedlec | Poland | Zielona Góra | 1992 |