The 30-year-old, who featured only sporadically for Tana Umaga's Blues in 2017 as he battled injury and form issues, has agreed to a two-year deal with La Rochelle in the French Top 14 competition.
Ranger, who has made 76 appearances for the Blues, previously played for Montpellier in France from 2013-15, before returning to the Auckland franchise in 2016 in an ill-fated bid to revive his New Zealand career.
