People living in the Republic of Ireland have voted in favour of same sex marriage.
It's the first country in the world to let the people vote on the issue.
Up until now two men or two women were not allowed to marry each other but now that's changed.
Almost two million people voted, with 62% voting yes.
But lots of people disagreed, including the Catholic Church.
Those against it say marriage has been between a man and a woman for hundreds of years and shouldn't be altered.
Around the world
Attitudes towards gay people vary across the world.
Currently 20 countries allow same sex marriage.
But in some others it is illegal just to be openly gay - more than 70 countries have laws against same-sex couples including Iran and Nigeria.
In India being gay was decriminalised in 2009 but changed back to a crime again in 2013.
In 2012 Russia banned gay pride events for 100 years.
In the UK, gay marriage is allowed in Scotland, and England and Wales, but there are no plans to bring a law to allow it in Northern Ireland.