Northwest Passage, a long-sought water route through or around the northern part of North America, connecting the Atlantic and Pacific oceans. Early explorers hoped such a route would shorten voyages from Europe to Asia.

John Cabot, in 1498, and probably his son Sebastian Cabot, in 1508, were the first to search for the passage. John Davis, Martin Frobisher, and William Baffin made explorations in the next century. While in search of the passage, Henry Hudson discovered Hudson Bay in 1610.

Other explorers searched for a river system leading through North America. The St. Lawrence River-Great Lakes system was explored in the hope of finding westward links to the Pacific Ocean. Samuel Hearne's overland trip to the Arctic Ocean, 1770–72, proved that no strait or river led from Hudson Bay to a western ocean. As a result of the overland journeys to the Pacific by Alexander Mackenzie (1792–93) and Lewis and Clark (1804–06) it became obvious that the only location for a northwest passage would have to be in the far north of Canada.

In 1819 William Parry sailed through Lancaster Sound and Melville Sound, passing north of Victoria Island. After crossing 110° west longitude, a new record, he was forced by impassable ice to turn back. In 1847 Sir John Franklin's expedition found a passage south of Victoria Island, but all members died before getting any opportunity to sail through it.

Robert McClure traversed the Northwest Passage from west to east during 1850–54, but not entirely by water. His ship became icebound at Banks Island, and he and his crew walked the remaining distance to a rescue ship.

The passage was first successfully navigated by Roald Amundsen, aboard his vessel Gjöa. He entered the passage through Baffin Bay in 1903; passing by way of Franklin's route, south of Victoria Island, he completed the passage in 1906. The next successful trip was a 28-month journey made from west to east by Henry Larsen in his ship St. Roch , 1940–42; the return trip took 86 days. Afterward, many vessels, including United States submarines, navigated the Northwest Passage.

The discovery of oil in 1968 on Alaska's North Slope resulted the following year in the United States oil tanker Manhattan becoming the first commercial vessel to make the voyage through the passage. The trip was made to test the feasibility of shipping oil by that route. The possibility of using the passage for shipping touched off a dispute between the United States and Canada—the United States claiming the passage to be an international waterway, Canada claiming sovereignty over much of the route. The dispute remained unresolved through the 1990's.