Rantzau
Amt
Flag Coat of arms
Map of district of Pinneberg highlighting Rantzau
Country	Germany
State	Schleswig-Holstein
District	Pinneberg
Region seat	Barmstedt
Government
• Amtsvorsteher	Matthias Bagger
Area
• Total	112.0 km2 (43.2 sq mi)
Population  (2020-12-31)
• Total	8,905
Website	www.amt-rantzau.de

Rantzau is an Amt ("collective municipality") in the district of Pinneberg, in Schleswig-Holstein, Germany. It is situated around Barmstedt, which is the seat of the Amt, but not part of it. The Amt was named after the County of Rantzau, which existed between 1649 and 1864.

The Amt ("collective municipality") Rantzau consists of the following municipalities:

1. Bevern
2. Bilsen
3. Bokholt-Hanredder
4. Bullenkuhlen
5. Ellerhoop
6. Groß Offenseth-Aspern
7. Heede
8. Hemdingen
9. Langeln
10. Lutzhorn