This year saw Luxembourg, the United States and Ireland all legally recognise same-sex marriage.
Looking only at Europe, a map recently posted to Imgur has shown how the opposing views to same-sex marriage on the continent changed legal recognition in countries over the years.
The map paints a picture of a sharp geographic divide between Eastern and Western Europe over the issue.
The Netherlands was the first country to legalise same-sex marriage in the world, followed by Belgium.
England and Scotland legally recognised same-sex marriage in 2014, followed by the Republic of Ireland in 2015.
View our interactive timeline of same-sex marriage in Europe, below:
Northern Ireland voted in favour of gay marriage in November, but the motion failed after the Democratic Unionist Party vetoed any change in the law.
The DUP used a petition of concern to defeat a vote of 53 to 52 in favour of same-sex marriage, arguing that the law change did not command sufficient cross-community support.