| Official Name: | Hasslö |
| Pushpin Map: | Sweden Blekinge#Sweden |
| Subdivision Type: | Country |
| Subdivision Name: | Sweden |
| Subdivision Type3: | Municipality |
| Subdivision Name3: | Karlskrona Municipality |
| Subdivision Type2: | County |
| Subdivision Name2: | Blekinge County |
| Subdivision Type1: | Province |
| Subdivision Name1: | Blekinge |
| Area Footnotes: | [1] |
| Area Total Km2: | 3.03 |
| Population As Of: | 31 December 2010 |
| Population Total: | 1,628 |
| Population Density Km2: | 537 |
| Timezone: | CET |
| Utc Offset: | +1 |
| Timezone Dst: | CEST |
| Utc Offset Dst: | +2 |
| Coordinates: | 56.1083°N 15.4625°W |
Hasslö (in Swedish pronounced as /ˈhâsːlœ/)[2] is an island and a locality situated in the Blekinge archipelago in Karlskrona Municipality, Blekinge County, Sweden with 1,628 inhabitants in 2010.
For many years, the Swedish navy's activities on Hasslö meant that foreigners' access to the island was restricted, but that is no longer true. Hasslö is famous for its fish, and fishing has historically been the main livelihood. A famous fishing site on Hasslö is the Rallbryggan.
Hasslö is a flat island and most of the people live near the coast. The island is connected to the mainland via the Hasslö Bridge.
Hasslö is the birthplace of the socialist Fabian Månsson (1872–1938), and today there is a statue erected of him on the island.
The following sports clubs are located in Hasslö: