| Slack | |
| Pushpin Map: | France#France Hauts-de-France |
| Mouth Coordinates: | 50.805°N 1.6014°W |
| Subdivision Type1: | Country |
| Length: | 22km (14miles) |
The Slack (in French pronounced as /slak/, in French pronounced as /s̟laːk/) is a 22adj=midNaNadj=mid coastal river in the Pas-de-Calais department, in northern France.
It rises at Hermelinghen on Mount Binôt, flows through Rinxent, Marquise, Beuvrequen, Slack (village near Ambleteuse) and flows into the English Channel in Ambleteuse next to Fort Mahon.