New York became the sixth US state to legally recognise the union of homosexuals after Govenor Andrew Cuomo signed an equality bill on Friday.
Taking to Twitter moments after the news, GaGa declared: "I can't stop crying. We did it kids...The revolution is ours to fight for love, justice+equality. Rejoice NY, and propose. We did it!!! (sic)"
The 'Edge Of Glory' singer also posted to the social networking site a snap of her celebrating the ruling with a group of friends.
Meanwhile, Harris, who is openly gay and has two surrogate-born children with long-term partner David Burtka, wrote: "It Passed! Marriage equality in NY!! Yes!! Progress!! Thank you everyone who worked so hard on this!! A historic night!"
Lesbian chat show host Ellen Degeneres echoed Harris's sentiment, tweeting: "I'm thrilled about the news from NY. Marriage equality! Every day we get a little closer. What an amazing feeling."
Ricky Martin, who came out as gay in March 2010, called for "a Time to celebrate!!! Marriage Equality for NYers! It's about... love!", while Lindsay Lohan and Cyndi Lauper both stated on Twitter that they were "proud" to come from New York.