The Fraser Canyon is a major landform of the Fraser River where it descends rapidly through narrow rock gorges in the Coast Mountains en route from the Interior Plateau of British Columbia to the Fraser Valley. Colloquially, the term "Fraser Canyon" is often used to include the Thompson Canyon from Lytton to Ashcroft, since they form the same highway route which most people are familiar with, although it is actually reckoned to begin above Williams Lake at Soda Creek Canyon near the town of the same name.^{[citation needed]}

The canyon was formed during the Miocene period (23.7–5.3 million years ago) by the river cutting into the uplifting Interior Plateau. From the northern Cariboo to Fountain, the river follows the line of the huge Fraser Fault, which runs on a north–south axis and meets the Yalakom Fault a few miles downstream from Lillooet. Exposures of lava flows are present in cliffs along the Fraser Canyon. They represent volcanic activity in the southern Chilcotin Group during the Pliocene period and the volcanic vents of their origins have not been discovered.

The canyon extends 270 kilometres (170 mi) north of Yale to the confluence of the Chilcotin River. Its southern stretch is a major transportation corridor to the Interior from the Coast, with the Canadian National and Canadian Pacific Railways and the Trans-Canada Highway carved out of its rock faces, with many of the canyon's side-crevasses spanned by bridges and trestles. Prior to the double-tracking of those railways and major upgrades to Highway 1 (the Trans Canada Highway), travel through the canyon was even more precarious than it is now. During the frontier era, it was a major obstacle between the Lower Mainland and the Interior Plateau, and the slender trails along its rocky walls, many of them little better than notches cut into granite, with a few handholds, were compared to goat-tracks.

North of Lytton, it is followed by BC Highway 12, then from Lillooet to Pavilion by BC Highway 99 (the farther end of the Sea-to-Sky Highway though it does not carry the name in that area). The British Columbia Railway (now operated by the CN) line follows the same stretch of canyon from Lillooet to just beyond Pavilion. Between there and the mouth of the Chilcotin River, there are only rough ranching roads, and the terrain is a mix of canyon depths flanked by arid benchland and high plateau. Between Pavilion and Lillooet, the river's gorge is at its maximum depth, with the river throttled through a series of narrow gorges flanked by high cliffs, though still flanked above those cliffs by wide benchlands which stand on the foreshoulder of the mountain ranges flanking the gorge.

At Hells Gate, near Boston Bar, the canyon walls rise about 1,000 metres (3,300 ft) above the rapids. Fish ladders along the river's side permit migrating salmon to bypass a rockslide that diverted the river during the blasting of the Canadian Northern Railway line in 1913. The area around Hell's Gate carries the name Black Canyon, which may either be a reference to the colour of the rocks when it rains, or the name of a community built on the cliffsides here during the Fraser Canyon Gold Rush. At the site that once housed railway workers, a tourist attraction was built in 1971 and takes visitors across Hell's Gate via an aerial tramway.

At Siska, a few minutes south of Lytton, there are the Cisco bridges, a pair of railway bridges at the throat of a rocky gorge. From south to north, the Canadian Pacific has been on the west side of the canyon, and the Canadian National has been on the east side. At Siska, the two railways switch sides: the CP—160-metre (520 ft) truss bridge—crosses to the east, the CN, on an 250-metre (810 ft) steel-arched bridge over the CP, is now on the west. The two railways now have an agreement to allow directional running through the canyon as far as Basque. All eastbound trains (CN, CP, and Via Rail's eastbound Canadian) run on the CP line. All westbound trains (CN, CP, Via Rail's westbound Canadian) use the CN tracks.

Just north of Lillooet, narrow rock ledges choke the river just at the confluence of the lower canyon of the Bridge River, forming an obstacle to migrating fish that has made this spot the busiest aboriginal fishing site on the river, from ancient times to the present. Concentrations of First Nations people here, from all tribes of the Interior, were believed to have been in excess of 10,000.

Many stretches of the Fraser are named in their own right, starting with the Little Canyon between Yale and Spuzzum, which is officially the lowest reach of the Fraser Canyon (although in regional terms Hope, 32 kilometres (20 mi) farther south, is considered a canyon town and to be the southern outlet of the canyon because the highway became more difficult from that point; the river is navigable to Yale). Between the Spuzzum and Boston Bar was known in the gold rush as the Big Canyon or Black Canyon; there are several named subcanyons of the Big Canyon, most famously Hells Gate Canyon (in some descriptions the Black Canyon is below Hell's Gate). Above the Big Canyon there are the Lillooet Canyon, Fountain Canyon, Glen Fraser Canyon, Moran Canyon, High Bar Canyon, French Bar Canyon and more all the way up to Soda Creek Canyon near Quesnel. Upstream from there the river flows in wider country, but in the Robson Valley between Prince George and Tête Jaune Cache, the river enters the Grand Canyon of the Fraser. The Black Canyon was the site of a shantytown of the same name, much of which was on catwalks on the ramparts of its dark-rock cliffs.