Zieluń-Osada was formerly part of the German Empire. In the German Empire, the place was called Zielun Stadt.
The place is now called Zieluń-Osada and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Zielun | Russian Empire | Mlava | 1914 |
| Zieluń | Poland | Mława | 1919 |
| Zielun Stadt | German Empire | Mielau | 1939 |
| Zieluń-Osada | Poland | Żuromin | 1945 |
| Zieluń-Osada | Poland | Ciechanów | 1992 |