Some users found that while the site was working fine on phone others couldn't access it either from phone or desktop.
Numerous thousands of users affected took to rival social network Twitter to complain about the lack of service.
It disrupted many people's routines.
Hundreds of Instagramusers are reporting problems with the United States social network website every minute, DownDetector data reveals.
Another person suggested, optimistically, that the fall of Facebook would mean "people might reset to baseline human status". According to The Mirror, the social media sites began having issues at 11:09 a.m.
Huge numbers of people posted problems with the website just after 4pm, with news feeds struggling to load.