Facebook, Instagram and WhatsApp were temporarily out of service early Sunday.
All three social media platforms, including Facebook Messenger, were affected by the outage.
Downdetector.com, a site that monitors site failures, shows that Facebook has been down since 6:30 am EST in much of the world, with thousands of reported failures concentrated in the northeastern United States, Europe and in the Philippines.
Most users appear to be operational again on Monday at 9:00 am Eastern Standard Time.
An email asking for a comment on the cause of the crash was sent to Facebook.
#FacebookDown, #instagramdown, and #whatsappdown were all trends on Twitter around the world.
Facebook acquired Instagram in 2012 and WhatsApp in 2014.
There are more than 1.52 billion active daily users on Facebook, according to the social media network's website.