The A84 autoroute is a major motorway in western France completed on 27 January 2003 to connect the cities of Rennes in Brittany with Caen in Lower Normandy.

It is part of the Autoroute des Estuaires from Belgium to Spain, avoiding Paris.

It is dual-carriageway both ways on its entire course and service areas are positioned at regular intervals.

The motorway was built with a special road surface to allow rain water to run off quickly, but it is ineffective with snow that often falls in large quantities in winter, so snowploughs are employed regularly.

The A84 is also to be extended to Nantes by upgrading the RN 137 dual-carriageway, thus creating a Caen-Rennes-Nantes route.