Peers backed a government bill paving the way for gay couples to marry. It is set to become law by the end of the week, with the first weddings in 2014.
Labour's Lord Alli said its passage meant "my life and many others will be better today than it was yesterday".
But Tory peer Lord Framlingham said the "ill-thought through" change had been "bulldozed" through Parliament.
Peers approved the principle of same-sex marriage last month, despite efforts by opponents to "wreck" the legislation.
MPs had earlier done the same, in the face of opposition from many Conservatives, the Church of England and other faith groups.
Supporters of the Marriage (Same Sex Couples) Bill wore pink carnations during Monday's proceedings in the Lords, during which a series of minor amendments - including one relating to pension benefits for same-sex couples - were proposed.
Government minister Lady Stowell said the bill "puts right something which is wrong" and had been improved by detailed scrutiny in the Upper House. "I can't claim to be a gay rights campaigner, but I am a firm believer in justice and fairness," she said.
But the Gay Marriage No Thanks group claimed it had been prevented from mounting an advertising campaign around Parliament after its truck was vandalised and its driver threatened.
After clearing the Lords, the bill will return to the Commons for a short debate on government amendments before the Commons begins its summer recess on Thursday. The bill must then receive Royal Assent before it becomes law.
Same-sex marriage in England and Wales is a step closer to becoming law after the House of Lords approved the change.