The North Pennines are the northernmost section of the Pennines, a range of hills which run north–south through northern England. They run along the border between County Durham and Northumberland in the east and Cumbria in the west, and are bounded to the north by the Tyne Valley and to the south by the Stainmore Gap. Much of the region is moorland, and it contains significant industrial archaeology.

The North Pennines have been designated a national landscape and a UNESCO Global Geopark.

Several major rivers rise in the North Pennines, including the Tees and Wear. The part of the area in County Durham, including Teesdale and Weardale, is known as the Durham Dales.

The North Pennines are formed from a succession largely of sedimentary rocks laid down during the Palaeozoic era, later intruded by the Whin Sill and affected by glaciation during the Quaternary period.

Mud and volcanic ash deposited during the Ordovician and Silurian periods were buried and subsequently faulted and folded during the Caledonian orogeny, the mudstone becoming slaty. These rocks which are between 500 and 420 million years old are now exposed along the great scarp which defines the western edge of the area and also in an inlier in upper Teesdale. Unseen at the surface but proved in boreholes is the Weardale Granite, a batholith emplaced as molten rock into the slates and other rocks around 400 million years ago. Its presence beneath the region results in it being an upland area since granite is relatively less dense and therefore ‘buoys up’ the North Pennines. This uplifted area is known as the Alston Block and is partly defined by major faults; the Stublick and Ninety-Fathom faults to the north and the Pennine Fault to the west. To the south is the Stainmore Trough.

Overlying the early Palaeozoic rocks and granite are a succession of limestones, shales and mudstones dating from the Carboniferous period. At this time the part of the Earth’s crust which would later become England lay in the equatorial zone and was covered from time to time by shallow tropical seas. Repeated cycles of inundation led to the development of a series of cyclothems; the laying down of layers of limestone, shale and sandstone with occasional coal seams.

Shortly afterwards, (c. 295 million years ago) molten rock once again intruded the sedimentary succession, this time resulting in the emplacement of the doleritic Whin Sill within the Carboniferous sequence. Known as whinstone locally, it baked the rocks with which it came into contact, resulting in the Sugar Limestone found in upper Teesdale. Cooling of the sill itself resulted in the formation of columnar joints, characteristic of its outcrop at places like High Cup. The sill has been dated at between 301 and 294 million years old thus straddling the Carboniferous/Permian boundary.

Around the start of the Permian period, about 290 million years ago, mineral-rich waters, associated with the still warm granite, circulated within the Carboniferous succession and gave rise to mineral-rich veins which have formed the basis of a lead mining industry since at least Roman times.