Hecate Strait (/ˈhɛkɪt/; Haida language: K̲andaliig̲wii, also siigaay which means simply "ocean") is a wide but shallow strait between the Haida Gwaii (formerly the Queen Charlotte Islands) and the mainland of British Columbia, Canada. It merges with Queen Charlotte Sound to the south and Dixon Entrance to the north. About 87 miles (140 km) wide at its southern end, Hecate Strait narrows in the north to about 30 miles (48 km) It is about 160 miles (260 km) in length.
According to the BCGNIS, the southern boundary of Hecate Strait is defined as a line running from the southernmost point of Price Island to Cape St James on Kunghit Island, the southernmost point of Haida Gwaii. The northern boundary is a line from Rose Point, the northeastern tip of Graham Island, to Hooper Point at the north end of Stephens Island off the mainland.
Hecate Strait was named by Captain George Henry Richards in 1861 or 1862 after his surveying vessel, HMS Hecate.
Hecate Strait, because it is so shallow, is especially susceptible to storms and violent weather. The Haida crossed the Hecate Strait to the mainland to plunder coastal villages to take slaves and booty. Only the Haida knew the real nature of the Strait's workings, and so could not be followed by the tribes of the mainland. Hecate Strait, therefore, was one of the main defenses of the Haida people from attack.