| Image Coa: | DEU Appen COA.svg |
| Coordinates: | 53.6617°N 9.7444°W |
| Image Plan: | Appen in PI.svg |
| State: | Schleswig-Holstein |
| District: | Pinneberg |
| Amt: | Geest und Marsch Südholstein |
| Elevation: | 6 |
| Area: | 20.26 |
| Postal Code: | 25480–25482 |
| Area Code: | 04101, 04122 |
| Licence: | PI |
| Gemeindeschlüssel: | 01 0 56 001 |
| Divisions: | 3 |
| Mayor: | Hans-Joachim Banaschak |
Appen is a municipality in the district of Pinneberg, in Schleswig-Holstein, Germany. It is situated approximately 3 km west of Pinneberg, and 20 km northwest of Hamburg.
It is twinned with the village of Polegate, near Eastbourne in East Sussex, England.
The municipality is known for its annual Appen musiziert benefit concerts.