A group linked to the Church of Ireland is protesting a new clause set to be included on the statute book in Northern Ireland.
The group, Changing Attitude Ireland, is holding a rally at Belfast City Hall in opposition to the proposed 'anti-gay' conscience clause.
The clause, proposed by the Democratic Unionist Party (DUP), would allow an opt out of equality legislation in Northern Ireland on the grounds of religious conscience.
Canon Charles Kenny of Changing Attitude Ireland said: "Our Christian faith informs us that we are all equal under God and we oppose any attempt to make it easier for providers of goods and services in Northern Ireland to discriminate against gay people."
"The DUP proposal is misleading when it pits people of faith against those who are gay or who affirm gay people. The DUP proposal ignores the fact that many people of faith oppose discrimination against gay people," he added.
Similar rallies are also being held in Derry and Newry.
It is believed the law gained traction following legal action taken against a Christian-owned bakery.
The Equality Commission brought a civil case against Ashers Baking Company, after it refused to bake a cake with a pro-gay marriage slogan last year.