For the first time same-sex couples are now legally allowed to get married in England and Wales.
Politicians from the main parties have hailed the change in the law.
British Prime Minister, David Cameron said the move sent a message that people were now equal “whether gay or straight”, but some religious groups remain opposed.
Scotland passed a similar law in February; the first same-sex marriages are expected there in October. Northern Ireland has no plans to follow suit.
In an article for the Pink News website, the prime minister wrote: “This weekend is an important moment for our country.”
“It says we are a country that will continue to honour its proud traditions of respect, tolerance and equal worth.
The law change would encourage young people unsure of their sexuality, he added.
Liberal Democrat leader Nick Clegg said “Britain will be a different place” as a result.
He congratulated his party for being part of the reform, saying: “If our change to the law means a single young man or young woman who wants to come out, but who is scared of what the world will say, now feels safer, stronger, taller – well, for me, getting into coalition government will have been worth it just for that.”
Labour leader Ed Miliband congratulated gay couples planning to tie the knot.
“This is an incredibly happy time for so many gay couples and lesbian couples who will be getting married, but it’s an incredibly proud time for our country as well, recognising equal marriage in law,” he said.
However, he warned that the “battle for true equality” was not yet won. BBC