To the southeast, the Tjeldsund Bridge connects Hinnøya with Skånland municipality and the mainland across Tjeldsundet, and to the northeast is the Vågsfjorden, where Harstad shares a water border with Ibestad municipality.
Harstad meji na Bjarkøy proti severu, Kvæfjord proti zahodu in Tjeldsund (v administrativni regiji Nordland) proti jugu.