Rząśnik was formerly part of the German Empire. In the German Empire, the place was called Rzasnik.
The place is now called Rząśnik and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Rzasnik | Russian Empire | Pultusk | 1914 |
| Rząśnik | Poland | Pułtusk | 1919 |
| Rzasnik | German Empire | Ostenburg | 1939 |
| Rząśnik | Poland | Wyszków | 1945 |
| Rząśnik | Poland | Ostrołęka | 1992 |