Saunalahti (Finnish) or Bastvik (Swedish) is one of the newest apartment building districts in Espoo, Finland, located by the Kummelivuori hill between Kivenlahti and Kurttila, west of the Kauklahdenväylä road, on the coast of the Espoonlahti bay.

Saunalahti is separated from Kivenlahti by the Länsiväylä highway, continuing to Kirkkonummi as Jorvaksentie.

At some point, Bastvik was planned as a remote facility of the apartment fair held in Kauklahti in summer 2006.

The Bastvik manor had a significant sawmill in the 19th century, and because of this, Sågholmen (formerly an island, currently the Sahaniemi peninsula) has been a stopping place for large ships.

When the Kauklahti glass works went into bankruptcy, Nordstedt sold the farm to banker Antti Hiltunen and his family in 1928.