LGBT couples will now be able to marry, including those who held civil partnerships before the new legislation went into effect. Same-sex couples who married legally in other countries will also have their marriages valid in the country.
The BBC reports that the Marriage Act 2015 applies to civil marriages only, giving religious institutions the ability to turn down performing a marriage between same-sex couples.
Those who want to marry will have to submit their intent to do so five days in advance, according to New Zealand's News 3. About 2,054 couples have registered for civil unions since Ireland introduced that legislation in 2011, but the first legal same-sex marriage in Ireland since the new law's passing has yet to occur.
The BBC spoke to Orla Howard, a woman who married her wife in the U.S., about the law's passing.
"It's a terrific moment, because our marriage will be the same as any straight couple's marriage from Monday morning," Howard told BBC Northern Ireland. "It will bring all of the rights and protections that marriage brings, from the constitutional point of view, to our family and that's one of the key things for us."