They have shaped the Scottish landscape over thousands of years, carving out valleys and providing protection against invaders.
The length of a river is determined by the distance between its source and where it exits into the sea.
These measurements can prove controversial, with disagreements about where rivers start and end, the exact location of a source, and when a river turns into an estuary or firth (a particular problem in measuring the Forth River).
So, while no list may keep everybody happy, here’s our take on the 10 longest rivers in Scotland.
1. River Spey
One of the world's more famous salmon fishing rivers, the River Spey travels from Loch Spey in the Highlands to the North Sea. It's roughly 107 miles long, making it the second longest Scottish river, although some people insist the next river in our list is slightly longer. Photo: Canva/Getty Images
2. River Clyde
Coming in a around 106 miles, the River Clyde is either the second or third longest Scottish river, depending on who you listen to. In rises in the Lowther Hills of South Lanarkshire and flows past Glasgow - where it was home to the city's shipbuilding industry - into the Atlantic at Inverclyde. Photo: Canva/Getty Images
3. River Tweed
Another great salmon river, the The River Tweed rises at Tweed’s Well in Tweedsmuir, eventually flowing into the North Sea at Berwick-upon-Tweed 97 miles later. Photo: Canva/Getty Images
4. River Dee
Rounding out the top five is the River Dee. It originates in the Wells of Dee, in the wilderness of the Cairngorms National Park, and flows into the North Sea at Aberdeen 87 miles later. Photo: Canva/Getty Images