Balshaw will join Leicester Tigers centre Ayoola Erinle at the 2006 Heineken Cup finalists from next season after the former Wasps player also agreed a move to France following two seasons in the East Midlands.
Tom Palmer, James Haskell and 2009 Lion Riki Flutey have all also penned deals with French clubs, while Newcastle's Tom May and Bristol's Joe El Abd are the latest players to follow suit.
Balshaw went into the 2001 Lions tour of Australia as one of the form players in Britain and Ireland but played second fiddle to Bath team-mate Matt Perry for the majority of the tour.
The then 22-year-old did appear in all three Lions Tests against the Wallabies as a replacement, however, before going to win the World Cup with England two years later.
Balshaw was named in his second successive Lions party in 2005 but was forced to withdraw from the squad as a result of injury prior to departure for New Zealand.
Now 30 years old, Balshaw currently has 35 England caps to his name but has not featured for his country since the 2008 Six Nations.