As of today sam-sex couples will be able to register to marry in Northern Ireland.
Those already married will now have their marriage legally recognised.
Northern Ireland had been without devolved government for over 1000 days with Sinn Fein and DUP clashing over a number of issues resulting in a collapse of the power-sharing agreement.
In the absence of an assembly an amendment was introduced in July and backed by Westminster MPs to decriminalise abortion and extend rights to same-sex marriage to Northern Ireland if devolution had not been restored.
Stormont had not been restored and so the wheels were then put in motion to formally introduce the amendment.
Heterosexual couples will also be able to enter into civil partnerships from today. However, those already in civil partnerships will not be able to convert into marriage just yet with the Northern Ireland Office undertaking a consultation later this year about the subject.