Facebook has yet to offer an explanation for the outage.
Social media giant Facebook appears to be in the midst of recovering from an overnight disruption leaving millions worldwide without access.
The company – which also owns image-sharing site Instagram – has been experiencing issues with online messaging and posting across both sites.
The problems began on Wednesday afternoon, only showing signs of real recovery on Thursday morning.
"We're aware that some people are currently having trouble accessing the Facebook family of apps," Facebook said in a statement.
"We're working to resolve the issue as soon as possible."
Facebook's apps seemed to be recovering on Thursday morning, with Instagram announcing it was back.
In response to rumours posted on other social networks, the company said the outages were not a result of a Distributed Denial of Service attack, known as DDoS - a type of cyber-attack that involves flooding a target service with extremely high volumes of traffic.
However, Facebook users – of which there are around 2.3 billion monthly users today – are still experiencing difficulties this morning.
Facebook Workplace, the service used by businesses to communicate internally, is also experiencing problems.