The forward scored twice from the penalty spot before completing his hat-trick in the second half, helping Nice claim their second consecutive league victory and move provisionally into seventh place.
Rennes, who started the matchday in second position, suffered another setback in their pursuit of league leaders Paris Saint-Germain.
Wahi puts Nice ahead twice
Nice made an aggressive start and were rewarded in the 12th minute when Wahi won and converted a penalty to give the hosts the lead.
Rennes responded almost immediately, with Sebastian Szymanski heading home Mahamadou Nagida's cross in the 15th minute to make it 1-1.
The hosts regained the advantage in the 34th minute after Jonathan Clauss was fouled inside the penalty area. Wahi stepped up again and confidently converted his second spot-kick of the evening.
Nice continued to threaten before half-time, and Clauss extended their lead in the 45th minute of added time, finishing after good attacking work from Wahi.
The hosts went into the break with a deserved 3-1 advantage.
Amoura and Dia add to the goals
Nice increased their lead seven minutes into the second half when Mohamed Amoura finished a well-worked attacking move involving Sofiane Diop to make it 4-1.
Rennes attempted to fight their way back into the contest, and Boulaye Dia converted a penalty in the 58th minute to reduce the deficit to 4-2.
The visitors pushed forward in search of another goal, but Nice remained dangerous on the counter-attack. Rennes also had a goal disallowed for offside after Nagida found the net.
Wahi completes his hat-trick
The decisive moment arrived in the 73rd minute when Wahi completed his hat-trick.
Gauthier Hein provided the assist, allowing the Nice forward to find the net for his third goal of the night and seal a convincing 5-2 victory.
Wahi's outstanding display included three goals and an assist, making him the clear standout performer.
The 23-year-old, who is on loan at Nice from Eintracht Frankfurt, has now scored five goals and provided two assists across his last three appearances, underlining his growing influence in the team's attack.
Nice climb as Rennes lose ground
The victory represents Nice's fourth win in their last five matches and extends their unbeaten home run to nine consecutive games.
They moved provisionally into seventh place in the Ligue 1 standings, while Rennes remained second but missed the opportunity to close the gap on PSG.
For Nice, the result provides further encouragement as they look to build momentum. Rennes, meanwhile, will need a response after suffering another damaging defeat in their pursuit of the league leaders.
Match details
• Competition: Ligue 1, Matchday 9
• Fixture: OGC Nice 5-2 Stade Rennais
• Date: Friday, 30 October 2026
• Venue: Allianz Riviera, Nice
• Nice scorers: Elye Wahi 12' (pen), 34' (pen), 73'; Jonathan Clauss 45+2'; Mohamed Amoura 52'
• Rennes scorers: Sebastian Szymanski 15'; Boulaye Dia 58' (pen)
• Man of the Match: Elye Wahi