MPs have voted in favour of the Marriage (Same Sex Couples) Bill, allowing the draft legislation to clear its first parliamentary hurdle.
It means same-sex couples will be able to get married in both civil and religious ceremonies, where a religious institution has formally consented, in England and Wales.
Couples who had previously entered into civil partnerships will be able to convert their relationship into a marriage.
But what do people make of the decision?
Darren McCabe, in a civil partnership with Derek Hay since 2008
I'm over the moon, I saw the result as it came through on the news, it sent tingles down my spine. This is an historic day.
Gay marriage, or as I like to refer to it, same-sex equal marriage is important to not only me, but many other LGBT (lesbian, gay, bisexual, and transgender) folk across the country as it will mean we will finally have full equality. Civil partnerships, while all good and offer a lot of the same benefits as marriage, are still not 100% equal to the straight counterpart.
The love that I have for my civil partner is no less to the love my father had for my mother. Yet society seems to want to treat me like a lesser individual.
I go to work, I pay my taxes. I have no children and have no desire to have them, yet I get nothing back from the state for this. The only thing I get is to be treated as some kind of second-class citizen and abused verbally by many because I am gay. Allowing same-sex marriage will enhance society and we will become more tolerant of others.
It will also help the economy by providing more jobs to the hospitality sector which has seen massive job cuts in recent years. Not to mention the financial boost it could bring to struggling retailers. People seem to underestimate the value and strength of the pink pound - many LGBT folk will have larger disposable incomes.
Some things that will definitely not happen with the passing of this bill:
1. The world will not crumble
2. Society will not implode on itself
3. Family life will not alter
4. Straight marriages will not be devalued in anyway
Same-sex marriage will not affect anyone else, but for those who are entering into it. The same way that a straight marriage does not affect me.
Reverend Malcolm Brown, director of mission and public affairs for Archbishops' Council, Church of England
The parliamentary debate prior to the vote was made up of misinformation on both sides, with some honourable exceptions on both sides.
This bill has not yet gone to the House of Lords so we shall see if they make better sense of it.
The Church of England does not see gay people as a threat and is not attacking them.
The Church is against gay marriage because changing the definition and understanding of marriage will affect the whole of society.
One of the intrinsic aspects and social understandings of the union of marriage centres on the creation of children.
Gay couples can be excellent parents but it's not the same as having the biological inheritance of both parents passed on to the child. The meaning of marriage through the years has always helped secure that relationship between parents and their children as a socially good thing.
The understanding of marriage, that has existed for centuries and is enshrined in the Bible, is for the good of society. You tamper with that at your peril.
And while the emphasis of marriage has changed over the centuries and it now stresses personal companionship more strongly, but its definition has never altered. This legislation will change that in a way that will tend to make children less important.
If it comes into law, we will have to work very hard to make sure that families and children remain important and biological families will have to be shored up in other ways.
The Church of England can be followed on Twitter @c_of_e
Paul Parker, Recording Clerk for Quakers in Britain
This is the change in the law we have been seeking since 2009, when Quakers decided to recognise same-sex marriages. It is good to see that ministers and MPs have listened and voted for equality.
We are excited to see this bill. Three and a half years ago Quakers decided that same-sex couples should be able to marry in a Quaker meeting. Since then we have been waiting for the law to catch up. Today that has come a step closer.
Quakers around the country have been encouraging their MPs to vote for the bill. We see this vote as a vote for equality. Quakers see God in everyone and that leads us to say that all committed relationships are of equal worth and so we wish to celebrate them in the same way.
We welcome the discussion this has opened about marriage. We believe this change will enrich the institution of marriage because it will encompass all who endeavour to maintain stable, committed relationships.
Quakers worship in inclusive meetings, where all committed loving relationships should be witnessed and spiritually celebrated as marriage. We believe all are born equal and our love is equal too. We welcome this law, knowing that it is right for us, and that it will not be imposed on other faith bodies who do not yet share our view.
British Quakers can be followed on Twitter @BritishQuakers
Ed Costelloe, former chairman of Somerton and Frome Conservative Association
Over half the Conservative party have not voted for this. That's catastrophic for the prime minister in terms of political management.
It's self-inflicted too, because there's other ways of doing this that would not have caused this kind of ruction. He could have asked a royal commission to look into this and report back around the time of the next election in 2015.
Concerns about the issue of gay marriage were first raised to me within my member constituency about a year and a half ago.
All of my officers and the branches they represent, as far as I know, are against it. I've spoken to about 90 members of the association and three were neutral - everybody else was against it.
I wrote to various leaders of the Conservative party and did not get a satisfactory response, so I resigned my post in January as I felt so strongly about it. Other resignations are starting to mount.
There's anger and frustration about the way it's been done, as much as with the issue of gay marriage itself.
It seems very strange politics to upset your members so much that they leave.
I'm personally against gay marriage on religious grounds, but absolutely endorse civil partnerships, which I think give all the legal rights of marriage.
Anthony Wells, YouGov associate director
However much attention it is getting in the media at the moment, gay marriage is not the sort of issue that will have a big impact on people's votes come the general election when, as usual, people's votes will be decided upon the bigger issues.
Polls claiming to show that it will change a large number of votes are because the question asked singles out just that one issue. By May 2015, (when the election is due) gay marriage will have been on the statute book for two years and will be broadly accepted. More importantly, it will fade to insignificance next to bigger issues like the economy, health, crime and the merits of the party leaders.
Our most recent polling shows only 7% of people say that gay marriage would be an important issue in deciding their vote, and they are evenly split between people who support and oppose the issue.
The more important impact will be on how the Conservative party is perceived: in or out of touch, modern or stuck in the past, or - as our present polling and today's vote suggests - just hopelessly divided.
YouGov can be followed on Twitter @YouGov
Dr Sharon James, Coalition For Marriage campaign group
We're absolutely delighted at the scale of those MPs who voted against this. It's way more than we thought it would be at the start of our campaign.
It's not a good idea for society to move away from the time-honoured position of marriage as a union between a man and a woman.
The Coalition For Marriage welcomes civil partnerships, but we have been hearing from people who don't think the government created marriage, and don't have the right to redefine it.
There's no mention of this in the Conservative manifesto and this issue has been brought in out of the blue. And they're pushing it through in a profoundly hasty way.
In Spain, where same-sex marriage is allowed, the rates of marriage have plummeted by about 20%.
And civil liberties of those who disagree in countries with same-sex marriage have been eroded. Having it in law means consequences for freedom.
Charities, teachers and parents who disagree with it and want to withdraw children from schools, for example, are all facing litigation for their views.
I'm disturbed to hear many MPs say that people are writing to them to say they disagree with gay marriage, but that they're wrong. Those MPs are holding their constituents in contempt.
However, I was pleased to hear in the parliamentary debate that some MPs talked of being flooded with letters and emails from people against gay marriage, and that those MPs are listening.
This isn't a done deal, it's the beginning of a parliamentary process.
The Coalition for Marriage can be followed on Twitter @c4mtweets