Facebook, Instagram and WhatsApp were temporarily down early Sunday.
All three social media platforms, including Facebook Messenger, were affected by the outage.
Downdetector.com, a site that monitors site outages, shows Facebook had been down since 6:30 a.m. EST in much of the world, with thousands of reported outages concentrated in the northeastern U.S., Europe and the Philippines.
It appeared to be back up and running for most users by 9 a.m. EST.
A Facebook spokesman declined to give a reason for the outage, but said the issue has since been resolved and the company apologized for any inconvenience.
#FacebookDown, #instagramdown and #whatsappdown were all trending on Twitter globally.
Facebook acquired Instagram in 2012 and WhatsApp in 2014.
There are more than 1.52 billion daily active Facebook users, according to the social media network's website.