Gmail, Google Drive and Meet, and other online services appear to have stopped working, the Independent reported.
Google said that it was aware its users were having problems and was working to understand the cause of the outage.
Not all of the services are entirely broken. Some users are able to load Gmail as normal, for instance – and others can access their messages, but are unable to send them.
Google's problems came at the same time as issues at Slack, which said that some of its customers "may have trouble loading new messages or connecting to Slack". As with the Google outage, the problems do not appear to be affecting all of the service's users.
A post on Google's status page indicated it was aware of the problems and was still "investigating".
"We're investigating reports of an issue with Gmail. We will provide more information shortly," it said, with another, later update indicating that the investigation was still ongoing.
The page showed problems with Gmail, Google Drive, Google Docs, Google Meet and Google Voice. The rest of its services – such as Calendar and Chat – continue to work as normal, it said.
Tracking website Down Detector showed vast numbers of issues with Gmail and Google's other services.