This is the southern part of the strait between the two largest islands in the archipelago Streymoy and Eysturoy. Tangafjørður stretches from the two small villages Selatrað og Hósvík on Eysturoy and Streymoy respectively and south to the headland Eystnes on Eysturoy and to the village Hvítanes on Streymoy. The depth in the strait is 60 - 70 metres. The northern part of the strait is called Sundini.
The underwater tunnel Eysturoyartunnilin lies below the seabed under Tangafjørður. The tunnel reaches its lowest point 187m (613ft) below sea level.