Judith Vazquez and Lol-kin Castaneda hope to marry soon
A law allowing gay and lesbian couples to marry comes into effect on Thursday in Mexico City.
The law, which was passed by the city's local assembly in December, gives gay people full marital rights, including the right to adopt.
Several gay couples are now expected to register to get married as early as next week.
Mexico City is one of the first capitals in Latin America to fully recognise gay marriages.
Judith Vazquez and partner Lol-kin Castaneda hope to become one of the first couples to marry under the new law.
"It's the end of our fight and the beginning of life in freedom in Mexico City," Ms Vazquez told the BBC.
"This is a great, historic moment for the whole of society in Mexico City," added Ms Castaneda.
With this law - and previous legalisation on abortion and some form of euthanasia - the Mexican capital has become a liberal and progressive island in what remains a mostly conservative nation, says the BBC's Julian Miglierini in Mexico City.
But local gay activists say homophobic attacks are still frequent across the country, where people continue to face discrimination in the workplace for being gay or are attacked when displaying public affection to a person of the same sex, our correspondent adds.
Both the Catholic Church and conservative groups oppose the legislation, and the centre-right government even tried to get a ruling by the Supreme Court to block Mexico City from issuing gay marriage licences; they have so far been unsuccessful.
Despite the move in the capital, a gay marriage law at a federal level in Mexico remains unlikely.
Judith Vazquez says: "Our real battle is with our people in Mexico... Now we will have to leave our symbolic closet because we will be [considered] citizens and we have to go out to live in freedom."
In Latin America, only Uruguay has legalised civil unions nationwide and allowed same-sex couples to adopt children.
A handful of cities - in Argentina, Ecuador and Colombia - allow gay unions.
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