Halsön, or Halsögrund, is an island in the north of the Swedish sector of the Bay of Bothnia, in the Skellefteå archipelago.

Halsön is about 10 kilometres (6.2 mi) south of Byske on the mainland, just west of the larger island of Romelsön.

[3] Halsön is covered by forest plantations, but has three bays of environmental interest.

Kvällsmålsviken is in the shoal area between Romelsön and Halsön, surrounded by fine meadows and coastal hardwood.

These flads are very productive due to naturally high levels of nutrients, ample light and relatively warm water, supporting rich fauna and flora.