Grampians, the, or Grampian Mountains, highest mountain system of Great Britain, extending northeast to southwest along the southern fringe of the Highlands, central Scotland. Ben Nevis (4,406 ft/1,343 m) is the tallest peak. The scenic Grampians, extensively forested, have many lakes and contain the headwaters of many of Scotland's rivers. Numerous hydroelectric power plants are found there. The Grampians are a popular vacation area.