The pontiff says the teaching of gender theory is “ideological colonisation”.
Pope Francis has blasted the teaching gender theory in schools – calling it “insidious indoctrination”.
Speaking aboard the papal plane, the pontiff said that although he respects the LGBT community, he does not want children learning about gender identity.
“It is one thing for a person to have this tendency, this option, and even change sex,” he said.
“But it is another thing to teach it, gender theory, in schools along these lines in order to change mentality.
“I call this ideological colonisation.”
He later said that Jesus would “certainly not” turn his back members of the gay community.
“Life is life, and things should be taken as they come,” he said.
However, the Pope said he was unwilling to “sanctify transsexuals”.
“I can see the front pages of papers now,” he joked.
“It is a moral question, and it must be resolved as best as possible, always with the mercy of God.”
This is not the first time the pontiff has spoked out against gender studies, claiming the growing acceptance of gender fluidity and the trans community “terrible” earlier this year.
“Today, in schools they are teaching this to children – to children! – that everyone can choose their gender,” he told bishops in August.
Francis added that the increased visibility of trans people is due to “ideological colonising” – which he believes is “terrible”.
Pope Francis is seen by many as progressive in terms of acceptance of the LGBT community, after saying the Church should apologise to gay people in June – but clearly, these sentiments have a breaking point.
Just last month, he praised anti-LGBT activists in Mexico, who took to the streets to protest same-sex marriage.