Osiek was formerly part of the German Empire. In the German Empire, the place was called Oschek.
The place is now called Osiek and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Osiek | Russian Empire | Plonsk | 1914 |
| Osiek | Poland | Płońsk | 1919 |
| Oschek | German Empire | Plöhnen | 1939 |
| Osiek | Poland | Płońsk | 1945 |
| Osiek | Poland | Ciechanów | 1992 |