The 79-time capped hooker joined the French Top 14 team in 2015, the day after the World Cup in England, alongside his brother, prop forward Jannie.
The brothers had played together in the Springboks’ 2007 World Cup winning squad.
In his five seasons at Montpellier, Bismarck Du Plessis has played 90 times scoring 26 tries.
Montpellier were in eighth place in the Top 14 table when the season ended early due to the coronavirus.
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