Koivusaari (Swedish: Björkholmen) is an island and a district of Helsinki, Finland.
Koivusaari is the westernmost district of the entire southern part of Helsinki. Directly west from it is a bridge across the Keilalahti bay, crossing the municipality border to Espoo, after which comes Keilaniemi, the easternmost district of southern Espoo.
Koivusaari metro station will be a Helsinki Metro station when the Länsimetro extension is implemented, most probably in early 2013. It will then become Helsinki's westernmost metro station.