[7] The town is located on the northeastern part of the large island of Hinnøya, along the Vågsfjorden.

The city is made up of several areas (bydeler) including Gansås, Grønnebakkan, Kanebogen, Medkila, Sama, Seljestad, Stangnes, and Trondenes and more.

On 1 January 1904, the village of Harstad was granted town privileges as a ladested.

During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee.

It is called Hárstták when it is spelled alone, but it is Hársttáid suohkan when using the Sami language equivalent to "Harstad municipality".