| Old Dutch Waterline New Dutch Waterline | |
|---|---|
| Netherlands | |
 William III of Orange inspects the Waterline during the Franco-Dutch War | |
| Type | Defensive line |
| Site information | |
| Controlled by | Netherlands |
| Site history | |
| Built | 1629–1815 (Old) 1815–1940 (New) |
| In use | 1629–1940 |
| Materials | Flooded plains, sluices, earth walls, brick, concrete, steel |
| Battles/wars | Third Anglo-Dutch War |
The Dutch Waterline[1][2] (Dutch: Hollandsche Waterlinie, modern spelling: Hollandse Waterlinie) was a series of water-based defences conceived by Maurice of Nassau in the early 17th century, and realised by his half brother Frederick Henry. Combined with natural bodies of water, the Waterline could be used to transform Holland, the westernmost region of the Netherlands and adjacent to the North Sea, almost into an island. In the 19th century, the Line was extended to include Utrecht.
On July 26, 2021, the line was added to the Defence Line of Amsterdam to become the Dutch Water Defence Lines UNESCO World Heritage Site.