| Bos | |
| Mouth Location: | Nahe |
| Mouth Coordinates: | 49.5644°N 7.093°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Germany |
| Subdivision Type2: | State |
| Subdivision Name2: | Saarland |
| Length: | 5.8km (03.6miles) |
| Source1 Elevation: | 490m (1,610feet) |
| Mouth Elevation: | 379m (1,243feet) |
| Basin Size: | 12634km2 |
Bos is a river of Saarland, Germany. It is a left tributary of the Nahe, which it joins in Gonnesweiler.
The Bos originates at the Zallenberg at an elevation of 490m (1,610feet) above sea level. From here, the stream flows predominantly to the east. It passes the village of Bosen, part of Nohfelden, on the north and then, after about 3.4km (02.1miles), it reaches the Bostalsee. Just before the reservoir it is joined by the right tributary Pärwiesbach which reaches it after flowing through Bosen. Its mouth is located about 300m (1,000feet) south of the village of Eckelhausen, also part of Nohfelden. The outlet of the Bostalsee is located southwest of Gonnesweiler. South of the Bostalsee the Dämelbach flows into the Bos. After only about a further 1km (01miles) the Bos joins the Nahe on the left at an elevation of 379m (1,243feet) above sea level.
On its 5.8adj=midNaNadj=mid course, the Bos drops 111m (364feet), which corresponds to a mean bottom slope of 1.91%. It drains a 12634km2 drainage basin.