People were forced to use candles last night and were unable to access the internet after SSE Power Distribution suffered a major network transmission failure.
Many homes were yet to be reconnected by midnight as engineers attempted to repair the damage.
The electricity supply to Inverness was cut for about 30 minutes, causing disruption to rail services in and out of the Highland capital.
Passengers on an early-evening train from Wick were marooned on board for four hours, while the 5.41pm train from Edinburgh to Inverness ground to a halt two hours into its journey. All services between Aberdeen and Inverness were disrupted.
Among the worst-affected areas was Orkney, where residents were plunged into darkness. In Kirkwall, businesses reported losing power from 9.30pm for one hour and there were similar problems in outlying areas.
One employee at the town's Albert Hotel said: "The power suddenly just went off and we couldn't get on the internet to find out what was going on.
"All the people in the bar were sitting having their drinks by candlelight. There was a bit of a Dunkirk spirit, but we thought it would only last a few seconds - not an hour."
In Stornoway, pubs and hotels reported the lights had gone out for 30 minutes. The power failure also affected Shetland. Residents on Skye suffered 90 minutes of disruption.
SSE Power Distribution said in a recorded message on its customer helpline it was "experiencing a major transmission network fault problem affecting in excess 100,000 properties".
The voicemail added: "Our engineers have been mobilised to primary locations across the country and have begun the process of restoring supplies.
"Due to the nature and scale of the fault we are not able to confirm details of the restoration of supplies."
The statement added that it expected most supplies would have been reconnected by midnight, but this could not be guaranteed.