The second-rower was set to come off-contract at the end of the 2022 season, however, has inked a two-year extension to stay at Redfern.
The deal comes just days before the November 1 deadline, when all 16 clubs, as well as the NRL's newest franchise in the Dolphins are allowed to begin negotiating with off-contract players for the 2023 season.
Koloamatangi has been one of the NRL's breakout stars over the last 24 months, culminating with a grand final appearance and call-up to the New South Wales State of Origin reserves list for the third game of this year's series.
He may only have 37 games under his belt, but he has made himself a weapon in attack for the Rabbitohs and recently ranked second in Zero Tackle's most effective ball-runners list.
All Run Metres
Koloamatangi is a Rabbitohs' junior and said he wants to stay at the club for as long as he can.
“Souths is my junior club and I want to stay here for as long as I can,” Koloamatangi said.
“We made the grand final this year and that experience has made me hungrier than ever to win a premiership.
“I think we have an opportunity to do that here in the short term with the players and the coaches we have and I want to be part of helping this Club win its 22nd premiership.
“I love this Club. I feel comfortable here and I know the Club has my best interests at heart which makes me want to do my best every chance I get to represent Souths.
“I’m achieving some of my personal goals here too and I’m ready to take my game to the next level next season.
“I’m really happy to be extending my contract and I can’t wait for Season 2022 to get underway.”