Regierungsbezirk Zichenau was a Regierungsbezirk, or administrative region, of the Nazi German Province of East Prussia in 1939–45. It is also referred to as South East Prussia (German: Südostpreußen). The regional capital was Zichenau (Ciechanów).
The government region was created on 26 October 1939, out of Polish areas annexed by Nazi Germany during World War II. The region had an area of 12,000 km² and a population of approximately 895,000, including 800,000 Poles, 80,000 Jews, and 15,000 Germans.
- Mackeim district (Maków)
- Mielau district (Mława)
- Ostenburg district (Pułtusk)
- Plöhnen district (Płońsk)
- Praschnitz district (Przasnysz)
- Scharfenwiese district (Ostrołęka)
- Schröttersburg district (Płock)
- Sichelberg district (Sierpc)
- Zichenau district (Ciechanów)