Gay couples will be able to get married from Saturday 29 March, 2014, the government announced on Tuesday.
The date, which is 109 days from now, is understood to be several months earlier than initially anticipated by the government.
Culture secretary Maria Miller said: "Marriage is one of our most important institutions, and from 29 March 2014 it will be open to everyone, irrespective of whether they fall in love with someone of the same sex or opposite sex."
"This is just another step in the evolution of marriage and I know that many couples up and down the country will be hugely excited that they can now plan for their big day and demonstrate their love and commitment to each other by getting married."
Upon hearing the news, Ben Summerskill, the chief executive of gay rights campaign group Stonewall tweeted: "Hurrah! Same-sex marriages in England and Wales from 29 March 2014!!"
The gay marriage legislation piloted through the Commons by Miller and personally backed by David Cameron was highly controversial - with the majority of Tory MPs voting against it. However it managed to make its way into law thanks to the support of Lib Dem and Labour MPs.
Same-sex weddings in some British consulates and armed forces bases overseas will be possible and arrangements for ceremonies in military chapels will be in place from June 2014.
The Department for Culture, Media and Sport said couples wishing to be among the first to marry will need formally to give notice of their intention to marry on 13 March 2014.