It's unclear at this time what caused the problem, which lasted around 30 minutes.
At around 1 p.m. ET on Monday, Facebook stopped working for users, and people aren't sure why.
Did you have trouble accessing your Facebook feed?
"Facebook is down?" wrote one user. "We quickly investigated and restored access for everyone".
DownDetector.com showed outages spanning all over the country, with a major outage reported on the east coast.
Many took to social media websites like Twitter to report the outage. Still more people were reporting issues in parts of Mexico, Europe, and South America, with concentrations in Peru and Argentina.
Currently, the hashtag is a trending topic in U.S., Nigeria and worldwide. Similar messages greeted people using the Facebook app. A look at the real-time outage map on Down Detector suggests the social network is down for a large chunk of the USA, especially along the eastern seaboard.
Facebook has 1.49 billion daily users, according to public information posted by the company, itself.