The world's largest online social network also gives its users the option to list themselves as single, married, in an open relationship or "it's complicated," among others.
The option for civil unions or domestic partnerships is only available to Facebook users in the U.S., Canada, the U.K., France and Australia, said the nonprofit Gay & Lesbian Alliance Against Defamation, which has been among the groups working with Facebook to add the options.
Facebook said it is rolling out the feature in countries where users asked for it.
"We will monitor user reaction and requests, and assess how to move forward with the rollout based on how this is going, and respond," said Facebook spokesman Andrew Noyes in an e-mail statement.
Facebook has well over 500 million users. About 70 percent of them live outside of the U.S.
