Same sex couples will be allowed to apply to marry in Uruguay from Monday, nearly four months after a bill was approved by the country's Congress.
President Jose Mujica signed the legislation in May but it was only due to enter into effect 90 days later.
About half a dozen couples should apply for dates at civil registry offices in the coming days, activists say.
Following Argentina in 2010, Uruguay became the second South American nation to pass same-sex marriage legislation.
Across Latin America, the number of countries allowing gay unions or marriages is growing.
In Brazil, the council that oversees the country's judiciary said offices could not deny the issue of civil union documents when gay couples wanted full marriage certificates.
However, the issue still requires a bill to be approved by the Congress.