The Denison River is an 84-kilometre wilderness river in Tasmania, Australia, flowing through one of the most remote and wild landscapes in the country before joining the Gordon River. The river is not easily accessible and reaching it demands a significant commitment: trips typically begin at Strathgordon, where paddlers drive to the north-west corner of Lake Gordon (Pearce's Basin), paddle approximately 20 kilometres across the lake, then undertake a multi-hour scrub bash of around 3 kilometres over a range to reach the river itself. A rough path marked with pink tape assists with navigation over this portage, though the approach remains demanding.

Once on the river, paddlers can expect a mix of flatwater sections and whitewater, with rapids requiring regular scouting from the bank or via careful eddy-hopping. One notable hazard is a section where the entire river disappears beneath an enormous boulder field, with only a small unrunnable chute remaining — this feature requires a portage and demands careful attention. Scouting rapids is standard practice throughout, and paddlers should be prepared to communicate using river signals and whistle blasts.

The Denison passes through the Truchanas Nature Reserve, which protects one of the largest remaining stands of Huon Pine and is named after photographer and environmentalist Olegas Truchanas, who first explored the river in the late 1960s. The river eventually joins the Gordon River, from which paddlers continue downstream to Sir John Falls and on to Heritage Landing, covering roughly 100 kilometres in total over approximately seven days. Exit options include pickup by West Coast Yacht Charters or Gordon River Cruises, with the latter delivering paddlers to Strahan.

The experience is defined by extreme isolation, silence, and intact wilderness. Wildlife, river sounds, and dramatic scenery characterise the journey. The trip is multi-day by nature and is suited only to experienced paddlers comfortable with remote self-sufficiency, whitewater, and extended off-track travel. Supplies for around six days are typically carried. The overall character of the Denison is that of a serious expedition river in a largely unvisited part of Tasmania's south-west wilderness.