Gmail was first launched in April 2004 and to the public in 2007
Google's email service Gmail, used by millions of around the world, has been out of action since around 10.15am.
Google has released a statement saying: "A number of of users have had difficulty using Gmail.
"We're working to resolve the problem. We know how important Gmail is to users, so we take issues like this very seriously, and apologise for the inconvenience."
The spokesman said the problem was not universal but was widespread.
When users try to log in to their accounts they get a message saying "the Gmail server has encountered a temporary error and could not complete your request. Please try again in 30 seconds".
Online reports on Twitter and other technology websites say users are still able to access email via their desktop inboxes and phones suggesting the problem is related just to the Gmail website.
It's unclear whether the crash is affecting only the UK or the whole world.
Gmail was launched by Google in April 2004 but only became available to the general public in February 2007.
The service remains in beta "testing" status despite the service now having millions of users.