"Love is love!" Spears, 27, said on her Twitter page Tuesday. "People should be able to do whatever makes them happy!"
Cyrus, 16, also Twittered to blogger Perez Hilton (who famously asked Miss California Carrie Prejean the controversial question during Sunday's Miss USA competition) after he informed the teen queen of the high suicide rates among gay and lesbian youth.
"Jesus loves you AND your partner and wants you to know how much He cares!" Cyrus said. "Like I said, everyone deserves to be happy."
Later, she added, "I am a Christian and I love you - gay or not - BECAUSE you are no different than anyone else! We are all God's children."
Heidi Montag of "The Hills," who is marrying Spencer Pratt this weekend, even weighed in.
"God says in the Bible that we should love our neighbor and He created us all as equals," she said on Twitter. "I know in my heart that gays and lesbians should have the same government rights that Spencer and I will when we get married. So, yes, this blonde Christian believes in gay marriage."