The "Northwest Passage" was the nickname given by the USS Voyager crew to a narrow corridor of space devoid of Borg activity even though it cut through the heart of their territory. The region was filled with intense gravimetric distortions caused by a large numbers of quantum singularities.
In late 2373, the Voyager crew intended to traverse Borg space at the Northwest Passage to avoid engaging the Collective. However, they soon discovered that the region lacked Borg activity because the quantum singularities had been created by Species 8472 as entry points for their invasion of the galaxy from fluidic space. As Species 8472 were more powerful than the Borg and intended to annihilate all life in the galaxy, Captain Janeway decided to avoid the Passage and instead ally with the Borg to defeat Species 8472. (VOY: "Scorpion")