MySpace, which lets users create a personalised homepage with photos, music and videos, has more than two million visitors each month.
There was no reason given on the website for what had caused the power outage at the data centre for the service.
A MySpace spokesman is reported to have said: "The data centre that MySpace and other companies use to host their sites has suffered from a power failure.
"Its engineers are working to solve the problem, and we hope it will soon be up and running again. In the meantime we apologise to our users for any inconvenience caused."
The service being offline, even for a short time, will be a blow for News Corp and MySpace in such a competitive global environment.
