Scottish Tory leader Ruth Davidson will give the "positive message" about gay marriage during a speech in Belfast.
Northern Ireland is the only part of the British Isles where same-sex marriage remains outlawed, and Ms Davidson insists people living there should be "afforded the same rights as everybody else".
The MSP, who recently became engaged to her partner Jen Wilson, will discuss the issue when she gives a lecture as part of Belfast's Pride celebrations.
Ms Davidson said she is "honoured" to have been invited to give the Amnesty Pride lecture.
"As a practising Christian, a protestant and a unionist who is engaged to a Catholic Irishwoman, for me, equal marriage isn't about one religion, country or community," she said.
"It is about people in Northern Ireland being afforded the same rights as everybody else.
"Scotland is a better place today because of equal marriage and I want to take that positive message from our experiences here to Belfast and beyond."
Last year, Ms Davidson was involved in the successful campaign for equal marriage to be introduced in the Republic of Ireland.
However, Northern Ireland's devolved Stormont Assembly has repeatedly refused to legislate on the contentious issue.
Although a slim majority of MLAs voted in favour of lifting the ban when it was debated for a fifth time last November, the proposal fell when the Democratic Unionist Party (DUP) deployed a controversial voting mechanism to effectively veto it.
Those opposed to gay marriage argue that same-sex couples already have the ability to enter into civil partnerships and claim there is no appetite for further change.
The matter is also being contested through the courts where two same-sex couples have challenged the current law under human rights legislation.