Churches and state buildings here and in the UK will be lit up today as part of a campaign to highlight religious intolerance.
Waterford, Sligo, Armagh and Derry Cathedrals are taking part in the #RedWednesday initiative as well as Knock Basilica.
In the UK, the Houses of Parliament and The Palace of Westminster are among dozens of public buildings which will be brightly illuminated.
We stand in faith and freedom to shine a light on the discrimination and violence faced by millions of Christians around the world today –the most oppressed of all faith groups in the world. They are always in our prayers and never forgotten! #RedWednesday https://t.co/gVoMVy8prD pic.twitter.com/retCNTS91l— Christ the King (@ctkcov) November 19, 2017
It is the brainchild of two organisations which advocate for Christians around the world.
John Newton from 'Aid the Church in Need' says it is a chance to show solidarity.
Mr Newton said: "Around the world members of various faiths are persecuted because of their beliefs. They suffer rape, they suffer torture, they are killed because of what they believe.
"People may have seen the situation with the Rohingya muslims over in Myanmar, the Christians in Iraq along with the Yazidis and Mandaeans, and they have suffered extreme persecution by extremist groups because of their faith."