Miley Cyrus, who last year got a tattoo in support of gay rights, tweeted: "@NOH8Campaign we're one step closer beautiful people :) #Prop8IsUnConstitutional."
"Woohoo! Die Prop 8 Die!!!" Olivia Wilde added. "9th Circuit just ruled you unconstitutional. Next step Supreme court."
Meanwhile, Kelly Osbourne also chimed in, tweeting, "Are my ears hearing this correctly? If so my eyes are filling with tears of joy! Thank you lord #Prop8IsUnconstitutional."
The ruling is a huge victory for those in support of same-sex marriage, but only applies in the state of California. Proponents of Prop. 8 have said they will appeal the decision.
"Today's ruling finally clears the field for an appeal to the United States Supreme Court, where we are confident we will be victorious," the Save Prop 8 campaign said in a statement.
What do you think about the issue? Let us know your thoughts in the comments.