According to troubleshooting site Downdetector, the social media site first reported problems at just after 12.20am Tuesday morning UK time.
The site showed there were more than 32,000 incidents of people spotting issues with Instagram.
Most of the issues with the service were reported in the United States and the UK.
Users also complained about the site in Australia and New Zealand.
A spokesman for Instagram said they were aware of an issue causing Instagram to be down for some users, and were working quickly to fix it.
“Instagram acting up again”
Traypostedthat, Twitter user
They didn’t specify how many users had been affected by the issue.
Many took to other social media sites such as Twitter to express their frustration.
One user, Traypostedthat, tweeted: “Instagram acting up again.”
Another user, Laur, wrote: “Leaving Instagram and coming onto Twitter to make sure it’s not just my Instagram that’s down.”
A third user tweeted: “Oh my god I logged out of all my accounts, deleted Instagram, and restarted my phone because I thought something was wrong with it.”
Some said the site seemed to be patchy but not completely down.
One user in Indonesia told Daily Star Online two of the three accounts they managed were down, but a third was still working.
Later on Tuesday morning, the site confirmed in a statement Instagram was fully functional again.
It didn’t give a reason for the shutdown and didn’t specify how many people were affected.
The statement also didn’t say which regions had faced problems.
Instagram is one of the most popular social media platforms in the world.
It has more than one billion active monthly users, according to website Statista.