Rice is best known for writing "Interview with the Vampire" and other Gothic romances.
The writer was raised Catholic, but said she regarded herself an atheist for many years before converting back to Catholicism in 1998, The Guardian said.
"In the name of Christ, I refuse to be anti-gay. I refuse to be anti-feminist. I refuse to be anti-artificial birth control. I refuse to be anti-Democrat. I refuse to be anti-secular humanism. I refuse to be anti-science. I refuse to be anti-life. In the name of Christ, I quit Christianity and being Christian. Amen," the author wrote on her Facebook page.
"I remain committed to Christ as always but not to being 'Christian' or to being part of Christianity," she added. "It's simply impossible for me to 'belong' to this quarrelsome, hostile, disputatious, and deservedly infamous group. For 10 years, I've tried. I've failed. I'm an outsider. My conscience will allow nothing else."