The world's greatest bike race will start from western France for the first time since 2011, when the riders departed from the Vendee region.
The first stage will take the peloton on a 188km journey from Mont St Michel to Utah Beach.
The second stage will be a 182km ride from St Lo to Cherbourg and the third will start from Granville and finish at a destination which is yet unknown.
The whole route will be unveiled in October 2015.
The 2015 Tour de France will start from Utrecht, Netherlands, its fourth Grand Depart from abroad in six years.