Thousands of reports were registered throughout the country.
The issue began at around 3pm, according to outage monitor DownDetector.com
Some viewers complained on social media of sound problems and blurry images, while others claimed to not be able to view the channels at all.
“ITV has gone down so much interference no announcement to inform us why it’s happened,” one viewer wrote.
Freeview, which hosts ITV channels, responded to some complaints on Twitter, stating: “We are aware of issues with ITV channels just now. We do not have any more info as yet. We do recommend not returning.”
The outage comes amid warnings of a major geothermal storm in the Northern Hemisphere, with solar flares expected to cause disruption to power grids and satellites. It is not clear if the outages are related.
Service for ITV channels appeared to be returning shortly after 4pm.