Den Osse is a small hamlet and marina on the shore of the Grevelingenmeer, a large saltwater lake in the province of Zeeland, administratively part of Brouwershaven in the municipality of Schouwen-Duiveland.

With only around 15 permanent residences, it has developed primarily as a holiday and boating destination. The harbor serves as a popular access point to the Grevelingenmeer for recreational boating, sailing, and water sports.

It is also a well-known dive site: the area around the pier headland and the shallow sandy plain to its west offers encounters with beach crabs, pipefish, starfish, shrimps, North Sea crabs, and lobsters sheltering among basalt stones.

Entry is possible from the end of the pier or a small shell beach, though the entry point can be slippery. A campsite, mobile-home rentals, and a surf and swimming beach are located nearby.