The Hungarian parliament has passed a law effectively banning same-sex couples from adopting children.
The legislation put forward by Prime Minister Viktor Orban's right-wing government says only married couples can adopt, with some exceptions for single relatives of the child.
Same-sex marriage is illegal in Hungary, but adoption has been possible if one partner applies on their own.
One rights group called the new laws "a dark day for human rights".
What are the new rules?
Mr Orban has made sweeping changes to the Hungarian constitution since coming to power in 2010.
An amendment also approved on Tuesday defines family as "based on marriage and the parent-child relation. The mother is a woman, the father a man".
Same-sex couples will now be unable to adopt, even if one of them applies as a single person.
"The main rule is that only married couples can adopt a child, that is, a man and a woman who are married," Justice Minister Judit Varga said.
Single people will now require special approval from the government to adopt.
Parents must raise their children in a conservative spirit, the constitution now states.
"Hungary defends the right of children to identify with their birth gender and ensures their upbringing based on our nation's constitutional identity and values based on our Christian culture," it says.
The government says the changes are needed as "new ideological processes in the West" have made it necessary to "protect children against possible ideological or biological interference".
What has the reaction been?
The new rules have been strongly criticised by rights groups.
"This is a dark day for Hungary's LGBTQ community and a dark day for human rights," said David Vig, director of Amnesty Hungary.
Masen Davis, Executive Director at Transgender Europe, said: "We are deeply concerned for the health and safety of trans children and adults in Hungary in such a hostile climate."
Last week EU leaders reached a compromise with Hungary and Poland to avoid the two nations vetoing the EU's long-term budget over what they see as an attempt to impose liberal values on them.