The River Ashop is a 10-kilometre watercourse in the Derbyshire Peak District, England, draining a basin of approximately 49.5 square kilometres. Rising at Ashop Head on Black Ashop Moor on the eastern slopes of Mill Hill — roughly three miles southeast of Glossop and just north of Kinder Scout — the river flows eastward through remote countryside, broadly following the Sheffield to Manchester Snake Pass road before emptying into Ladybower Reservoir, which in turn drains into the River Derwent.

Paddling on the Ashop is only viable after heavy rainfall when the river runs in spate; under normal flows the water is too shallow to float a kayak. When levels are up, the river becomes highly technical, featuring numerous weirs and hydraulic holes. The channel is narrow and relatively shallow throughout, meaning the rocky riverbed poses a significant hazard to anyone who capsizes. The upper section carries the greatest volume and presents the most demanding whitewater, including a short but fast-moving tributary that passes through a steep tunnel beneath the road — by far the most challenging feature on the river.

Beyond the hydraulic hazards, paddlers must contend with a variety of in-channel obstructions. Fallen trees and fences crossing the channel are common and require careful negotiation. At high water, when the current is running fast, these features become genuinely dangerous. The combination of technical water, strainers, and a confined channel means the river demands a high level of competence and situational awareness.

The river's name derives from the Old English æsc-hop, meaning "Ash Valley," and the route passes through Snake Woodlands, a stretch of remote upland terrain characteristic of the Dark Peak. The surrounding landscape is open moorland and woodland, reflecting the wild character of the upper Derwent catchment. Given the river's dependence on rainfall and its short length, trips are necessarily brief and opportunistic rather than planned far in advance, and paddlers should be prepared for rapidly changing conditions in this upland environment.