With New Zealand poised to become the first country in the Asia-Pacific region to legalise same-sex marriage, here is a breakdown of nations with similar laws on the books:
NETHERLANDS: On April 1, 2001 the Netherlands became the first country in the world to legalise same-sex marriage, with the same rights as heterosexuals. Includes the right to adoption.
BELGIUM: Homosexual couples in Belgium have almost the same rights as heterosexuals. They won the right to marry in 2003 and in 2006 parliament voted into law a bill allowing homosexual couples to adopt children.
SPAIN: In 2005 Spain became the third member of the European Union to pass a law allowing same-sex marriages. Gay couples can adopt children, whether they are married or not.
CANADA: Canada adopted a national law allowing gays to marry and adopt in July 2005 though most provinces had already allowed same-sex unions before that date.
SOUTH AFRICA: The country legalised same-sex unions and adoptions by gay couples in November 2006, becoming the first African nation to do so.
NORWAY: A 2009 law allowed homosexuals to marry and adopt children. Civil partnerships have existed in the country for 20 years.
SWEDEN: Sweden's homosexuals have been allowed to wed in religious or civil ceremonies since May 2009.
PORTUGAL: Under a 2010 law Portugal legalised gay marriage, while excluding the right to adoption.
ICELAND: Prime Minister Johanna Sigurdardottir married her long-time partner in June 2010 as a new law legalising homosexual marriages came into force.
Same sex couples who have lived together for at least five years have had the right to adopt children since 2006.
ARGENTINA: Gays in Argentina became the first on the South American continent to be able to wed and adopt, after legislation passed on July 14, 2010.
DENMARK: Denmark, the first country in the world to allow gay couples to enter into civil unions in 1989, voted overwhelmingly in favour of allowing homosexuals to marry in the state Evangelical Lutheran Church in June 2012.
URUGUAY: Uruguay voted this month to allow same-sex marriages nationwide, making it only the second Latin American country to do so.
Gay couples can marry in nine US states, as well as in the capital Washington, while parts of Mexico and Brazil also allow same-sex marriage.
FRANCE: France's upper house Senate voted last week to approve a landmark bill granting homosexual couples the right to marry and adopt, putting the bill on track to become law within weeks.
BRITAIN: British lawmakers voted in February in favour of controversial legislation allowing gay marriage despite fierce opposition from members of Prime Minister David Cameron's Conservative party.
The bill must next be scrutinised by a committee of lawmakers and then go before the upper chamber the House of Lords before becoming law.
A number of other countries have adopted laws that recognise civil partnerships and give couples more or less the same rights as heterosexuals.
Countries to have recognised civil unions without yet accepting gay marriage include Germany (2001), Finland (2002), the Czech Republic (2006), Switzerland (2007) and Colombia and Ireland (both 2011).