Impassioned speeches were delivered in the chamber, by both supporters of the landmark vote, and critics who wanted to preserve the word 'marriage' for heterosexual couples.
The proposal survived two attempts to derail it and introduce civil partnerships or union civile instead. It was supported by 37 votes to seven.
Legislation now needs to be drawn up to enact the policy – that law will also need to be voted through. It will include an opt-out for churches.