Marais extends Bordeaux stay
Marais, 26, a former player with the Super Rugby side Sharks, arrived in France in 2013, and was given the role of vice-captain last season by coach Raphael Ibanez.
Since his arrival in western France he has played 61 Top 14 matches scoring seven tries.
Marais, who has never played for South Africa, will be eligible to play for France from July 1 next.
Agence France-Presse