A congress of New Caledonia's USTKE union has replaced its leader, Gerard Jodar, who had been at its helm for a decade.
Reports say the congress, which was held behind closed doors in a remote village, appointed the vice-president, Marie-Pierre Goyetche, following growing rifts in recent months.
Mr Jodar's term as leader was marked by a series of prolonged industrial conflicts.
Last June, he was imprisoned for his role in last May's violence at Noumea's domestic airport at the height of a protracted strike at the territory's domestic airline.
In January, an appeal court in New Caledonia ordered his immediate release.
His incarceration has been used by the union to campaign for changes at the territory's jail which is among the most overcrowded prisons run by France.