Reaching speeds of 320 kilometres per hour, the TGV train will link the French capital to the capital of the Spanish region of Catalonia in half the previous journey time.
The project has taken 10 years to come to fruition with delays in making trains compatible for use on both sides of the border and in laying track between the end of a tunnel linking Perpignan in south-west France to Figueras on the Spanish side.
Until now passengers have had to change trains at Figueras.
For now two trains will leave each city per day but the service is scheduled to double in January.
The new route will appeal to both business travellers and tourists, Mark Smith of train travel website Seat-61.com told RFI.
Although journey is twice as fast as before, the train follows a longer route in kilometres.
From Paris it goes south-east to Lyon before turning west in the Provence region.
It then speeds across the south of France before crossing the border and reaching its destination.
Unlike other international links from Paris, like as the Eurostar to London or Thalys to Brussels, the new service will not have a special name because of the cost of launching a brand.
The two rail companies expect a million passengers to use the service in 2014.