Gay and lesbian Facebook users can now state whether they are in a civil union or domestic partnership on their profile pages.
Groups had been set up to call for the change and the new options are being rolled out in the US, UK and several other countries today.
“This has been a highly requested feature from users,” Facebook communications manager Andrew Noyes said.
“We want to provide options for people to genuinely and authentically reflect their relationships on Facebook.”
LGBT rights groups said the move would help inclusion of gay couples.
Michael Cole-Schwartz, spokesperson for the Human Rights Campaign, said: “As LGBT people face a patchwork of relationship recognition laws, this gives people more tools to adequately describe their relationship.
“Facebook has been a company that has tried to be inclusive of the LGBT community and this just one sign of it.”
GLAAD said: “Today, Facebook sent a clear message in support of gay and lesbian couples to users across the globe.
“By acknowledging the relationships of countless loving and committed same-sex couples in the US and abroad, Facebook has set a new standard of inclusion for social media.”
The changes were developed with the help of gay groups such as GLAAD and the Human Rights Campaign and are available to users in the US, UK, Canada, France and Australia.