The Yorkshire Dales (also known as the "Dales") is the name given to an upland area, in Northern England.
The area lies within the historic county boundaries of Yorkshire, though spans the ceremonial counties of North Yorkshire, West Yorkshire, and Cumbria. Most of the area falls within the Yorkshire Dales District National Park, created in 1954, and now one of the twelve National parks of England and Wales (not including the South Downs which is due to become one).
The Dales is a collection of river valleys and the hills in between them, rising from the Vale of York westwards to the hilltops of the main Pennine watershed (the British English meaning). In some places the area even extends westwards across the watershed, but most of the valleys drain eastwards to the Vale of York - into the Ouse and then the Humber.
"Dale" comes from a Nordic/Germanic word for valley, and occurs in valley names across Yorkshire (and northern England generally) but since the creation of the Yorkshire Dales National park, the name "Yorkshire Dales" has come to refer specifically to these western dales (the area of dales and hills EAST of the Vale of York is now always called the "North York Moors" after the National Park created there). Confusingly, the Yorkshire Dales have plenty of moors, too. They tend to be glacial.