After initially going offline between 4pm and 5pm UK time Facebook and Instagram's apps began to come back online just past 11pm and WhatsApp at around midnight - around eight hours after the first outage hit.All three apps are owned by Facebook and share the same infrastructure.
"We are experiencing networking issues and teams are working as fast as possible to debug and restore as fast as possible."
Security experts speculated the problem came following network changes, with the cause still unconfirmed by late Monday evening.
The error message presented when attempting to access Facebook's website suggests it was a problem with Domain Name System (DNS).
DNS allows web addresses to take users to their destinations.
Adam Leon Smith, of BCS, The Chartered Institute for IT and a software testing expert, said: “The outage is caused by changes made to the Facebook network infrastructure.
“Many of the recent high-profile outages have been caused by similar network level events.
“It is reported by unidentified Facebook sources on Reddit that the network changes have also prevented engineers from remotely connecting to resolve the issues, delaying resolution.
“Notably, many organisations now define their physical infrastructure as code, but most do not apply the same level of testing rigour when they change that code, as they would when changing their core business logic.”
The website Downindicator began receiving reports of problems with Facebook's products around 4.30pm.
Downindicator also reported a sharp rise in reports of other popular websites going down like Snapchat and Gmail.
Data on its website showed that almost 80,000 people had reported the outages on Facebook.
ITV News North America correspondent Robert Moore reports on a difficult day for Facebook made worse, as the outage came the day after a whistleblower claimed in a US interview that the company prioritises its own interests over the public good.
Most complaints cited issues with the Facebook website (72%), while others were linked to issues with the server connection and the app.
More than 60,000 had complained about WhatsApp, with 43% reporting issues with the app itself, while 28% cited the server connection and 28% relating to sending messages.
More than 30,000 Instagram users also had similar complaints, with 51% relating to the app, 26% over the server connection and 23% citing the website.
A graph on the DownDetector website showed a clear spike from after 4pm.
With Facebook down people took to Twitter to complain about the issues.
In a tongue in cheek tweet, Twitter themselves posted "hello literally everyone."
Facebook Messenger was also impacted by the outage.
Facebook tweeted: "We’re aware that some people are having trouble accessing the Facebook app.
"We’re working to get things back to normal as quickly as possible, and we apologise for any inconvenience."
Whatsapp said on Twitter: “We’re aware that some people are experiencing issues with WhatsApp at the moment.
“We’re working to get things back to normal and will send an update here as soon as possible. Thanks for your patience.”
Instagram said: “Instagram and friends are having a little bit of a hard time right now, and you may be having issues using them. Bear with us, we’re on it.”
The company did not say what caused the outage.
There have also been reports of major US mobile networks AT&T, Verizon and T-Mobile going down.