The Alliance Party's ruling council has voted in favour of the introduction of same-sex civil marriage in Northern Ireland.
After months of consultation with party members and associations, a motion was passed on Saturday calling for equal civil marriage with robust protection for faith groups.
Leader David Ford MLA said: "Alliance has always stood for a progressive and equal society. Alliance will oppose any form of discrimination, whether it is based on age, race, disability, gender or sexual orientation.
"There are equality issues in allowing those in a same-sex relationship to have only civil partnerships, which is seen as discriminatory."
The motion also called for protection for faith groups, to ensure they are not forced to act contrary to their beliefs.
Mr Ford added: "Alliance is a democratic party, which is why we undertook a consultation process within our associations which lasted for several months."
The process was led by deputy leader Naomi Long.
She said: "After listening to Alliance Party members, as well as from people who have corresponded with me, I believe that we have made the correct decision in supporting the extension of civil marriage provisions to same-sex couples provided that robust protections are in place for faith groups who oppose these measures."