Frobisher Bay is a deep indentation in the extreme southeast coastline of BAFFIN ISLAND, over 230 km long and 40 km wide at the mouth, narrowing to 20 km towards its head. The configuration of the bay has a funnelling effect, so that the harbour of the city of IQALUIT, Nunavut, at the bay's head experiences a twice-daily tidal range of 7-11 m.

The bay's general physiography is the result of tectonic events associated with the rifting of the North Atlantic Ocean in the early Tertiary, during which time that part of the Precambrian Shield in the Frobisher Bay area was downfaulted and the blocks on either side were uplifted and tilted up to the northeast. An abrupt contact between these units is marked by the high cliffs rising from the bay, which because of the tilting are 330 m high on the north shore and twice that height on the south shore. Overdeepening occurred during the Pleistocene glaciation, when the Frobisher Bay trough was filled by a major outlet glacier from ice centered over FOXE BASIN.

The bay is named for Sir Martin FROBISHER, who discovered it in 1576. Believing that rock samples contained gold, he returned in both 1577 and 1578 with ever larger fleets to conduct mining operations that proved futile. He believed the bay was a strait, and it first appeared on maps as Frobisher Strait. The true nature of its physiography was not discovered until 1861 when the American Charles Francis HALL explored the area.