Do you know where same-sex marriage is actually legal? (Spoiler: it's hardly anywhere)

The Republic of Ireland would be the first country to legalise same-sex marriage through a referendum

The Republic of Ireland is expected to become the first country to legalise same-sex marriage through a referendum today, with a result set to be declared Saturday 23 May.

The referendum is being held 22 years after Ireland decriminalised homosexuality and five years after the government introduced legal recognition for gay couples.

Only 18 other countries worldwide have already legalised gay marriage, including the United Kingdom with the exception of Northern Ireland.

The United States and Mexico currently have regional legislation permitting same-sex marriage, but have yet to legalise throughout the country.

Laws pending in Slovenia are also expected to come into effect to legalise same-sex marriage, after a referendum against the bill. The referendum will only be successful if a majority of participants and at least 20% of all eligible voters vote against the law.

More than 3.2m people are being asked whether they wish to amend the country's constitution in the Republic of Ireland’s referendum.