Kullö is an island in the Stockholm archipelago in Sweden. It is situated in Vaxholm Municipality and Stockholm County.
In 2010, Kullö was also considered an urban area or locality, as defined by Statistics Sweden, and at that time had 889 inhabitants. In 2020 it was redefined as part of the Vaxholm urban area, and more recent population figures are no longer available.
Since 1965 the island has been crossed by , with a bridge to the south linking it to the island of Vaxön and the rest of the Vaxholm urban area. At the other end of the island, a bridge links to the island of Resarö and, via that, to the mainland.