Gay rights campaign group Stonewall heralded the Marriage (Sam Sex Couples) Bill as "an historic moment for lesbian, gay and bisexual people, their families and their friends".
After the Bill received royal assent, Stonewall released an image on Twitter with the words "Thank you Ma'am".
The group added, "This Bill will mean that, for the first time, children growing up to be gay in England and Wales will have full equality in law. We can now proudly claim to be a beacon to the world for gay equality."
More top news
The Duke of Cambridge became a fearsome samurai warlord - at least temporarily - when he visited the set of a long-running Japanese drama.
A grandmother says she was outraged after her grandson was segregated from his classmates by a cardboard screen - for being one minute late.
Leaked documents have revealed the first known picture of Mohammed Emwazi - named as IS militant Jihadi John - as a student in London.