BBC news reported they had been found in Bordeaux at 12.15pm after they went missing on Thursday last week.
Both Megan and Mr Forrest's parents have been told their children are safe.
But a Sussex Police spokesman said: "Mr Forrest has been arrested on suspicion of child abduction and Megan has been taken into protection.
"The information which led to them being located came as a direct result of media coverage in France. At this stage we are not confirming the specific location where they were found.
"Their families have been informed and arrangements will now be made for Megan and Jeremy's safe return."
The discovery came after the pair's parents made an emotional plea for either of them to make contact with the police.
It is being reported that police stopped the couple after a tip-off from a member of the public. They were stopped at 1.15pm French time, and split up from each other.
Mr Forrest could face up to five years in prison. Judicial authorities in Paris confirmed that he was arrested for 'the taking of a minor' against her parents' will.
Under France's penal code, this is punishable with five years in jail and a 75,000 euro fine.
Megan and Mr Forrest, a married maths teacher, have not been seen since they travelled to France last Friday from their homes in Eastbourne, Sussex.
The last confirmed sighting was from CCTV cameras on board the ferry from Dover to Calais at 9.30pm.