Widespread chaos was triggered when a tree fell and caused damage to overhead lines between Rugby and Milton Keynes on the West Coast Main Line, a spokesman confirmed.
Pictures shared on social media show hordes of people crammed inside the station, many of whom look frustrated due to the hour-long delays.
A disgruntled passenger wrote: “Euston station. A great place to be with young children waiting for an infinitely delayed train.”
Network Rail said its team is at the site near Long Buckby in Northamptonshire where the injury occurred.
Network Rail wrote on Twitter: “Due to congestion, #EustonStation is currently only an exit.
“All trains are currently suspended due to a felled tree causing damage to overhead lines.
“Passengers are currently advised not to travel – further updates ASAP.”
The company said it is working to remove the felled wood before assessing the damage and beginning repairs.
Travelers are advised not to go to Euston and instead check for regular updates.