Originally named simply Ísafjörður, the semantic run around happened through the -Deep meaning the inner parts of the fjord being reapplied throughout the innsea.
The fjord was named simultaneously with the island by Raven-Floke as he viewed it from a mountain from the south.
Ísafjörður, capital of the Westfjords region, is situated close to the mouth of Ísafjarðardjúp in Skutulsfjörður.
The north-eastern coast is fairly straight with the only inlet being Kaldalón, but the southern side has fjords extending well into the land: Skutulsfjörður, Álftafjörður, Seyðisfjörður, Hestfjörður, Skötufjörður, Mjóifjörður, Reykjafjörður and Ísafjörður.
Three islands lie in Ísafjarðardjúp: Borgarey, Æðey and Vigur.