A watermill or water mill is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding), rolling, or hammering. Such processes are needed in the production of many material goods, including flour, lumber, paper, textiles, and many metal products. These watermills may comprise gristmills, sawmills, paper mills, textile mills, hammermills, trip hammering mills, rolling mills, and wire drawing mills.

“Before mechanised sawing, constructing a modest merchant vessel required approximately ten sawyers working for three months,” writes Jaime Dávila in Forgotten. “With wind-powered sawmills, the same quantity of processed timber could be produced in less than a week.”

Thanks to their speedy mechanical saw, which turned logs into planks with almost no human effort, the Dutch could build ships faster than anyone else, which unleashed a century of Dutch maritime, economic and cultural dominance in Europe and the world.