Ralepelle, 26, will stay in South Africa until the end of the domestic Currie Cup season in October before heading to France.
"I always wanted to play abroad and this opportunity will provide that. I also feel that I will develop further as a rugby player in France, where different set skills will be required. I can only improve by playing over there," Ralepelle said in a statement released by the Bulls on Thursday.
The franchise's high herformance manager Janse van Rensburg also confirmed that negotiations with scrumhalf Jano Vermaak, who will make his Springbok debut against Italy on Saturday, are in progress.
"We are aware of the overseas offer made to Jano and this forms part of our negotiations," Van Rensburg said.
Ralepelle is the latest South African international to accept an overseas offer. Andries Bekker, Bryan Habana, Zane Kirchner, Juandre Kruger, JP Pietersen, Wynand Olivier and Morne Steyn have also signed deals to play outside South Africa in recent months.