A senior priest at the Vatican has revealed he is gay, on the eve of a major meeting that will define the Catholic Church's teaching on family.
Poland-born Krzysztof Charamsa said he wanted to challenge the Church's "backwards" attitude to homosexuality.
Msgr Charamsa, 43, said he was in a relationship and was "happy and proud" of his identity.
The Vatican called his actions "very serious and irresponsible" and stripped him of doctrinal responsibilities.
Msgr Charamsa's statement came as bishops arrived in Rome for a synod that will discuss homosexuality, among other issues.
In an interview with the Corriere Della Sera, Msgr Charamsa, said: "It's time the Church opened its eyes and realised that offering gay believers total abstinence from a life of love is inhuman.
Analysis: BBC's David Willey in Rome
There's the text and then there's the subtext. The official subject under discussion at the crucial three-week meeting of cardinals and bishops from around the world beginning at the Vatican on Sunday, chaired by Pope Francis, is how to ensure Catholic families heed Church teaching.
The ban on contraception, for example, is now honoured more in its breach than in its observance.
But the sudden revelation by a Polish Monsignore that he is gay, has a Catalan lover, and is apparently a member of a long-rumoured but never formally acknowledged "gay lobby" at the heart of the Catholic Church, risks skewing the smooth running of a long-anticipated event.
The subtext is whether the Church should relax its traditional hostility to same-sex partnerships and marriages in an age when even the Pope retorts: "Who am I to judge?"
Even though the gay Monsignore has not yet sent his letter of resignation to Pope Francis, the timing of his decision has raised a media storm that is unlikely to subside quickly.
And a book is in the offing which may reveal further details of his 12 years of hidden life inside the Holy See.
"I also know that I will have to give up the ministry," he added, but said he felt he had a duty towards sexual minorities to come out.
He has been a member of the Congregation for the Doctrine of the Faith - which is tasked with defending Church doctrine - since 2003.
The Vatican said he would no longer be able to be a member of the body, while his future as a priest would be decided by a local bishop.
In a statement it said: "The decision to make such a pointed statement on the eve of the opening of the synod appears very serious and irresponsible, since it aims to subject the synod assembly to undue media pressure."