Ireland legalised same-sex marriage after a majority voted in its favour during a referendum on May 23. In a landslide result, 62 per cent voted yes, outnumbering those who voted against it.
The country is the first in the world to legalise gay marriage based on popular vote.
There are, however, many other countries, as well as several states within the United States, where such marriages are already legal.
The Netherlands: April 1, 2001
The Netherlands was the first country to allow same-sex marriage when its Parliament voted 107-33 in favour. The law requires that at least one member of the couple be a Dutch national or to live in the Netherlands.
Belgium: June 1, 2003
Belgium became the second country to legalise gay marriage when King Albert II approved the Bill, which had previously been passed by the Senate and Chamber of Representatives. Ninety-one of the 122 deputies in the Belgian Parliament voted for the change, which stipulates that only couples from countries with the freedom to marry can be married under Belgian law.
Spain: July 3, 2005
In 2004, the newly elected Prime Minister, Jose Luis Rodríguez Zapatero from the Spanish Socialist Party, moved to legalise gay marriage. A majority of Spaniards supported the measure, and the Parliament voted 187 to 147 in favour. The law states that at least one partner must be a Spanish citizen in order to legally marry, although it also allows couples to marry if they have legal residence in Spain.
Canada: July 20, 2005
On June 28, 2005, the House of Commons in Canada passed the Civil Marriage Act, which was then passed by the Senate on July 19, 2005. The Civil Marriage Act, which received Royal Assent on July 20 that year, provided a gender-neutral definition of marriage. The national legislation passed after more than three quarters of Canadian provinces and territories legalised same-sex unions. Since marriage laws in Canada do not have residency requirements, same-sex couples who travel from the United States to Canada may also get married there.
South Africa: Nov 30, 2006
In December 2005, the Constitutional Court of South Africa ruled that denying marriage to same-sex couples violates the country's constitution and gave the Parliament one year to adjust laws to comply with the ruling. The court also made it clear enacting only a civil unions law would not work. On Nov 14, 2006, Parliament voted 230 to 41 to end the exclusion of same-sex couples from marriage in South Africa, making the nation the first in Africa to do so.
Norway: Jan 1, 2009
On June 11, 2008, members of parliament in Norway approved a Bill in favour of same-sex marriage by a vote of 84-41. Family Issues minister Anniken Huitfeldt said at the time: "The new law won't weaken marriage as an institution. Rather, it will strengthen it. Marriage won't be worth less because more can take part in it."
Sweden: May 1, 2009
On April 1, 2009, a majority of the Swedish Parliament voted in support of a Bill to make gay marriage legal. The proposal was approved after a landslide vote in which 261 members voted for and 22 voted against, with 16 people who did not vote. The new legislation took effect on May 1, 2009, replacing the legislation approved in 1995 that allowed gay couples to form a union in Sweden via registered partnership.
Portugal: June 5, 2010
In May 2010, Portugal's President Aníbal Cavaco Silva ratified a law that was passed in January 2010 by Portugal's parliament to allow same-sex couples to get married. The law was upheld as constitutional by the Portuguese Constitutional Court in April and was officially published in the official gazette of Portugal on May 31.
Iceland: June 27, 2010
On June 11, 2010, Iceland's parliament unanimously voted 49-0 to allow gay marriage. The Althingi parliament voted to add the words "man and man, woman and woman" to the country's existing marriage legislation. In 2009, the country became the first in the world to elect an openly gay head of state, when Johanna Sigurdardottir became the prime minister.
Argentina: July 22, 2010
On July 15, 2010, Argentina became the first country in Latin America to legalise same-sex marriage. The legislation was approved by a 33 to 27 vote, with three abstentions by the Argentine National Congress. It gives same-sex couples the same rights and protections as heterosexual couples, including the ability to adopt.
Denmark: June 15,2012
On June 7, 1989, Denmark passed a first-of-its-kind law allowing same-sex couples to receive the same legal and fiscal rights provided by marriage through registered partnerships. On Jan 18, 2012, the government introduced a gender-neutral marriageBill that legalised marriage between same-sex couples through civil registry or the Church of Denmark.
Brazil: May 14, 2013
On May 14, 2013, the National Council of Justice in Brazil ruled that government offices that issue marriage licenses have no standing to reject same-sex couples from marriage.
France: May 29, 2013
On April 23, 2013, the National Assembly in France took a final vote to approve the freedom to marry. The following month, on May 18, French President François Hollande signed the Bill into law. The Bill passed with overwhelming support in both houses - by a 331-225 final vote in the Assembly and 179-157 final vote in the Senate. The first wedding occurred in Montpellier.
Uruguay: Aug 5, 2013
On April 10, the lower House of the Uruguayan legislature approved a Bill to extend the freedom to marry to same-sex couples. Uruugay became the third country in Latin America to end the exclusion of same-sex couples from marriage nationwide when the law took effect on Aug 5.
New Zealand: Aug 19, 2013
On April 17, the Parliament in New Zealand took a final vote to approve a Bill for samesex marriage. The Parliament previously cleared the Bill on Aug 29, 2012, and March 12, 2013. Prime Minister John Key vocally supported the freedom to marry throughout the national conversation on why marriage matters. The first weddings between same-sex couples took place on Aug 19.
United Kingdom (England, Wales, Scotland): Feb 4 and March 29, 2014,
On July 17, 2013, the Queen of England granted royal assent to a Bill allowing same-sex marriage in England. The final approval came after the British House of Commons and House of Lords voted overwhelmingly in favour of the legislation multiple times. Same-sex couples in England and Wales were able to begin marrying on March 29, 2014. A marriage Bill was also passed Feb 4, 2014, in Scotland.
Luxembourg: June 18, 2014
On June 18, 2014, the Luxembourg Chamber of Deputies approved a Bill legalising same-sex marriage. The country's prime minister Xavier Bettel became the first European Union leader to enter a same-sex marriage on May 15, 2015.
Finland: Nov 28, 2014
On Nov 28, 2014, the Finnish Parliament approved an amendment legalising marriage between same-sex couples. The vote was passed with 105 members of parliament supporting it and 92 opposing. This amendment gave the same adoption rights to same-sex couples as heterosexual couples, as well. After this vote, Finland became the 12th European state to legalise marriage between same-sex couples.
United States: Several states have legalised same-sex marriage, although there is no blanket law that applies to the whole country
These are the states where same-sex marriage is legal: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, District of Columbia, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming
Sources: Time, freedomtomarry.org