Equality campaigners hailed a huge leap forward yesterday after same-sex couples in England and Wales finally won the right to walk their loved ones up the aisle.
Despite equal marriage laws passing through Parliament last year, couples could not even register their intention to marry until March 13.
The long wait for dozens of couples is over today as they walk down the aisle and take their vows in churches, registry offices and other venues.
Stonewall acting chief executive Ruth Hunt called it a "landmark moment for Britain."
She said: "We're delighted that so many people will be celebrating with happy couples up and down the country," she said.
"These marriages will send a powerful signal to every young person growing up to be lesbian, gay or bisexual. You can be who you are, love who you love and achieve anything you want - regardless of your sexual orientation."
Unison general secretary Dave Prentis said the change represents "a milestone in eradicating homophobia, biphobia and transphobia."
He said: "We welcome the new laws that allow couples to enter a same-sex marriage.
"For too long, LGBT families have been viewed differently and this has had a negative impact on all areas of their lives."
Despite overwhelming public support for the laws, equal marriage still has staunch opponents in the Church of England and Roman Catholic church.
Human rights campaigner Peter Tatchell insisted: "No ignorance or prejudice can hold back the triumph of love.
"Same-sex marriage is an unstoppable global trend because love and commitment are universal human traits, regardless of sexual orientation or nationality."
Quakers, the Movement for Reform Judaism and Liberal Judaism are among faith traditions who will marry same-sex couples.
But while same-sex couples in England and Wales can now marry and will soon be able to do so in Scotland, those in Northern Ireland continue to be denied the right after the NI Assembly voted not to overturn the ban last year.
Mr Tatchell added: "The legalisation of same-sex marriage ends the last major legal discrimination against gay people in England and Wales. Scotland will follow later this year. Sadly, Northern Ireland remains a bastion of homophobia."
Equality campaigners staged protests in both Belfast and Derry yesterday to demand legalisation.
Equal Marriage Campaign John O'Doherty said: "Equal marriage is about to become a reality in England and Wales.
"The Scottish Parliament has already voted overwhelmingly in favour of equal marriage and same-sex couples will be able to marry later this year.
"In the South of Ireland, a referendum is expected in the early part of 2015 and early opinion polls suggest a significant majority in favour.
"Twice before, an equal marriage motion has been debated in the Northern Ireland Assembly, losing by a small margin both times.
"We are demonstrating today to remind our political leaders and representatives that we do not want to be left behind in the march toward full legislative equality for LGBT people and their families."