| Arlau | |
| Subdivision Type1: | Country |
| Subdivision Type2: | Location |
| Subdivision Name2: | Nordfriesland, Schleswig-Holstein, Germany |
| Subdivision Type3: | Reference no. |
| Subdivision Name3: | DE: 9552 |
| Length: | 37 km |
| Source1 Location: | southeast of Sollwitt |
| Source1 Coordinates: | 54.5798°N 9.2511°W |
| Source1 Elevation: | 8 m |
| Mouth Location: | after crossing the Beltringharder Koog at the Holm Sluice into the North Sea |
| Mouth Coordinates: | 54.5281°N 8.8719°W |
| Basin Landmarks: | Villages: Behrendorf, Bondelum, Viöl, Arlewatt, Hattstedtermarsch |
| River System: | Arlau |
| Waterbodies: | Reservoirs: Arlau retention basin in the Beltringharder Koog |
| Custom Label: | References |
The Arlau (Danish: Arlå) is a 37-kilometre-long river in the county of Nordfriesland in Schleswig-Holstein, Germany. It flows into the North Sea near Nordstrand and is part of the Eider catchment.
The Arlau rises southeast of Sollwitt in North Frisia. It divides the Goesharde region into North and South Goesharde. Initially it flows a few kilometres south and runs along the municipal boundary of Behrendorf and Bondelum. About 3 km southeast of Behrendorf it changes course and heads in a westerly direction. The Arlau then flows south of Viöl and north of Arlewatt, crosses the Hattstedt Marsh and finally flows into the North Sea at the Beltringharder Koog at the Holm Sluice.
The Arlau is fed by the: