Norway's Lutheran Church voted in favour of same-sex unions.
At the Church's annual conference, 88 delegates out of 115 in total backed same-sex marriage. Under the new rules, priests who do not want to marry gay couples will still have the right to object.
"Finally we can celebrate love independently of whom one falls in love with," said Gard Sandaker-Nilsen, leader of the Open Public Church, a religious movement within the Church that had campaigned for a change in its laws.
The vote reflects increasingly liberal attitudes in wider Norwegian society to issues including homosexuality.
Norway became the second country in the world after Denmark to allow same-sex registered partnerships in 1993, and has allowed civil same-sex marriage since 2009.
Around 74 per cent of Norwegians were members of the Lutheran Church last year, according to the national statistics agency, but that number has been declining.
Last year, France's main Protestant Church voted to allow gay marriage blessings, while the US Presbyterian Church approved a change in the wording of its constitution to include same-sex marriage.
The Church of England, however, remains opposed. In January, the Primates meeting at Canterbury agreed to curtail the participation of the Episcopal Church of the United States (TEC) in Anglican Communion bodies for a period of three years as a result of its formal adoption of same sex marriage.
This attempt to appease conservative members of the Communion has faced difficulties, however. Kenya, Nigeria, Uganda and the province of Jerusalem and the Middle East boycotted an Anglican meeting in Zambia last week over concerns that the "consequences" imposed on the TEC had not been adequately carried out.
The Archbishop of Kenya, Eliud Wabukala, warned that "doctrinal confusion... has been allowed to take root in the Communion."
Additional reporting by Reuters.