The River Esk is a 28-mile river in North Yorkshire that rises on the North Yorkshire Moors and flows east — uniquely, it is the only major Yorkshire river to drain directly into the sea, entering the North Sea at Whitby Harbour between the West and East Piers. It retains its identity from source to mouth without joining another river, making it a first-tier river throughout its entire length. The river becomes tidal at Sleights, which marks the effective downstream limit for most whitewater paddling.

The river is graded 2–3 in normal conditions, rising to grade 4 in high water, so paddlers should assess river levels carefully before committing to a run. The most popular whitewater sections are Houlsyke to Egton Bridge and Egton Bridge to Sleights. Paddlers should be aware that conditions can change significantly with water levels, and the upper grades demand appropriate experience and skill.

The Esk flows through the Eskdale valley and passes through settlements including Castleton, Danby, Lealholm, Glaisdale, Egton Bridge, and Grosmont before reaching Sleights and ultimately Whitby. The river is almost entirely rural along its course, which contributes to notably clean water quality. The surrounding landscape forms part of the North Yorkshire Moors National Park.

Wildlife along the river is diverse and includes Atlantic salmon, sea trout, native brown trout, grayling, brook lamprey, water voles, otters, dippers, kingfishers, and sand martins. The Esk is the only river in Yorkshire, and one of only seven in England, to support a population of the endangered freshwater pearl mussel. The river has numerous salmon leaps, some artificially constructed to assist fish passage over weirs — paddlers should be aware of these weirs along the course.

In Whitby, the river passes through the harbour and into the sea, offering cultural and historical interest at the journey's end. Guided kayaking tours on the river are available in the area, with options running approximately 3.5 hours. Paddlers visiting Whitby around Ascension Eve may observe the traditional Penny Hedge ceremony on the east side of the upper harbour at 9am.