The Nelson River is a river of north-central North America, in the Canadian province of Manitoba. Its full length is 2575 km (1600 mile), it has mean discharge of 2370 m³/s (3100 yd³/s), and has a drainage basin of 982900 km² (379500 sq. mile), of which 180000 km² is in the United States. The river drains Lake Winnipeg and runs 644 km (400 mile) before it ends into Hudson Bay.
Besides Lake Winnipeg, its primary tributaries include the Grass River, which drains a long area north of Lake Winnipeg, and the Burntwood River, which passes through Thompson, Manitoba.
The river flows into Hudson Bay at Port Nelson (now a ghost town), just north of the Hayes River and York Factory. Other communities upriver from there include Bird, Sundance, Long Spruce, Gillam, Split Lake, Arnot, Crosslake, and Norway House.
The river was named by Sir Thomas Button, a Welsh explorer from St. Lythans, Glamorganshire, who wintered at its mouth in 1612, after Robert Nelson, a ship's master who died there. The area was fought over for the fur trade, though the Hayes River, whose mouth is near the Nelson's, became the main route inland.
Today, the Nelson River's huge volume and long drop make it useful for generating hydroelectricity. This has provoked bitter disputes with the First Nations of the area, whose lands past projects have flooded and future projects threaten.
Fort Nelson, an historic Hudson's Bay Company trading post, was located at the mouth of the Nelson River at Hudson Bay and was a key trading post in the early 18th century. After his pivotal role in establishing the Hudson's Bay Company, Pierre Esprit Radisson, noted French explorer, was chief director of trade at Fort Nelson during one of his sustained periods of service to England. Today, Fort Nelson no longer exists. Port Nelson, the abandoned shipping port remains on the opposite side of the river mouth on Hudson Bay.