Most Finns belong to the Evangelical-Lutheran Church (about 84%), while 1.1% belong to the Greek Orthodox Church.

The Evangelical Lutheran Church of Finland is a national church of Finland. It is part of the Lutheran branch of Christianity. The church is a member of the World Council of Churches and the Conference of European Churches. It is also a member of the Porvoo Communion and is actively involved in ecumenical relations.

Source: https://en.wikipedia.org/wiki/Evangelical_Lutheran_Church_of_Finland, http://finlander.genealogia.fi/sfhswiki/index.php/Customs_and_Traditions_in_Finland