Semi Kunatani, a standout performer for the Fiji team that won rugby sevens gold at the 2016 Rio Olympics Games, has signed a two-year deal with Castres, the French club announced on Thursday.
Back-rower Kunatani, 29, who also featured for his country at last year's 15-a-side Rugby World Cup, returns to the Top 14 after a stint with English side Harlequins.
His previous time in France was a three-season spell with Toulouse which coincided with when he struck gold with Fiji in Rio.
The 2018 French title winners announced 11 other new players for the coming season including Canada captain Tyler Ardron, Blue Bulls lock Ryno Pieterse and Kunatani's fellow countryman Vilimoni Botitu.
France's junior world champion lock Florent Vanverberghe and Uruguay scrum-half Santiago Arata are also heading to Stade Pierre-Fabre.
"They are players who have proved their quality and who still have great progress to make," coach Mauricio Reggiardo said in a statement.
"We think they correspond with the club's identity. It's now up to them to do what's needed to integrate."
The Top 14 season was declared over in April due to the coronavirus pandemic and earlier in the week it was announced no champion would be named.
Castres said in May their players would take a pay cut due to the financial impact of the COVID-19 outbreak with Toulouse, Toulon, Montpellier and Clermont following suit.
Castres-bound Fiji forward Semi Kunatani played two games at last year's Rugby World Cup