Karlsøya (Norwegian) or Gálsá (Northern Sami)[1] is an island in Karlsøy Municipality in Troms county, Norway.

[2] The one village area on the island is known as Karlsøy and in 2001, it had a population of 70.

The island is still the location of the historic Karlsøy Church.

The name Karlsøy comes from the man's name Kalfr which comes from Kalven, formerly meaning "the little island which lies next to the bigger one" (referring to Vannøya).

This article about an island in Troms is a stub.