Following widespread disruptions, Instagram was back online, according to the social media corporation.
At roughly 11 p.m. on Sunday, Down Detector, a service that records outages, received 56,628 incidents.
The UK outages were spread out on the Down Detector location map, with complaints of outages also arriving from the US and Australia.
At 1.19am on Monday, Instagram said that the problem that had caused the outage had been fixed.
Before 1am, the photo and video networking service looked to be operational once again, with less than 500 complaints of disruptions by that time.