Greece's parliament on Wednesday approved a bill granting same-sex couples the right to a civil union, becoming one of the last European countries to give them legal recognition after years of opposition from the influential Orthodox church.
A number of EU countries including Britain, France and Spain have legalised gay marriage, but some southern and eastern European states have made slower progress.
The new Greek law resolves property and inheritance issues, but makes no provision for the adoption of children.
"This is an important day for human rights," Prime Minister Alexis Tsipras told the chamber.
Tsipras said the bill gives same-sex couples "equal rights in life and death", terminating a practice of "backwardness and shame" for Greece.
Greece had been condemned for anti-gay discrimination by the European Court of Human Rights in 2013, after gay couples were explicitly excluded from a prior civilunions law in 2008.
"Instead of celebrating this, we should apologise to thousands of our fellow citizens," Tsipras said.
The law was supported by 193 lawmakers out of 249 present, with 56 voting against it.
Amnesty International hailed the move as a "historic step" but noted that lesbian, gay, bisexual, transgender and intersex (LGBTI) persons still faced hostility in Greece.
"Despite this first step, LGBTI people in Greece still live in a climate of hostility from which the authorities are failing to protect them adequately," said Gauri van Gulik, Amnesty International's Deputy Director for Europe and Central Asia.
"Physical attacks are on the rise, hate speech is common and goes unchecked by the authorities. Even displays of affection between same-sex couples are censored on television," van Gulik added.
Amnesty further pointed out that the law offers no gender recognition to transgender people.
In addition to Tsipras' left-wing Syriza party, the bill was supported by another four parties.
However the nationalist Independent Greeks (ANEL), who are part of the governing coalition, voted against the motion.
"The Greek constitution protects motherhood. Is there motherhood in men?" asked ANEL lawmaker Vassilis Kokkalis.
