A class 385 Express train left Edinburgh Waverley at 05:55, bound for Glasgow Queen Street. It is the first of 70 new electric trains which are expected to be running in the central belt by early next year.
Rail leaders are predicting that the introduction of the trains could have a transformational effect on Scotland's rail network.
Alex Hynes, the managing director of the ScotRail Alliance, said the introduction of the new trains will "trigger the transformation of the quality and capacity of Scotland's rail network".
He said he hoped that two new trains a week will be introduced to the ScotRail fleet over the next few months, before all 70 are in operation early next year.
It is part of a plan to reduce journey times between Glasgow and Edinburgh to 42 minutes by next year, and to provide 100,000 seats across Scotland every week day.