Haapasaari (Finnish: [ˈhɑːpɑˌsɑːri]; Swedish: Aspö) is an island and a former municipality of Finland in the former Kymi Province, now in the Kymenlaakso region.

[1] The island of Haapasaari is divided into two parts by a bay: Länsipää or Vestinpuoli in the west and Uustinpuoli in the east.

Haapasaari has a humid continental climate (Dfb) with moderation from the Gulf of Finland.Haapasaari has had some inhabitants since the medieval times, likely since the late 13th century following the Third Swedish Crusade, but a village on the island was first mentioned in 1547.

[6] The ancestors of the current inhabitants originated from nearby Vanhankylänmaa, migrating to Haapasaari in the 18th century or slightly earlier.

Researchers visited Haapasaari's disestablished school in 2011 to collect samples from ticks.

The researchers discovered that two out of a hundred sampled ticks carried the tick-borne encephalitis virus, twice as much as in other risk areas of Finland.