https://avoin-paikkatieto.maanmittauslaitos.fi/tiedostopalvelu/ogcproc/v1/

From the dataset abstract

NLS-FI INSPIRE Administrative Units Theme Dataset is a dataset depicting Administrative Units covering the land area and Maritime Units covering the sea area of Finland. Administrative Units contain the following INSPIRE feature types: AdministrativeUnit, AdministrativeBoundary. Maritime Units contain the following INSPIRE feature types: Baseline, MaritimeZone, MaritimeBoundary.

Administrative Units are updated once a year from the NLS Cadastral Index Map database. Maritime Units are quite stable and have no regular update cycle.

The dataset is available via the NLS-FI INSPIRE Download Service (WFS) for Administrative Units Theme and it can be viewed via the NLS-FI INSPIRE View Service (WMS) for Administrative Units.

Source: NLS-FI INSPIRE Administrative Units Theme Dataset