Alpine are last in the constructors' standings after 15 of 24 rounds and Gasly has scored all of their 20 points so far, with a highest placing of sixth in Britain.
A race winner, with victory at the 2020 Italian Grand Prix with Red Bull-owned AlphaTauri, the former F2 champion joined Alpine in 2023.
"I'm thrilled to commit my long-term future to Alpine. As a Frenchman, especially, driving for a French car company makes me feel very proud," said Gasly.
"I have always felt that this team is the right place to be for the future."
Gasly said the support of team leader Flavio Briatore and the commitment of newly appointed Renault CEO Francois Provost as well as the factory staff had made it a natural decision.
"I want to be here in years to come and deliver on our joint objective: to win races and world championships," he added.
Briatore, who led the team to titles when they raced as Benetton in the 1990s and then Renault in the early 2000s, referred to Gasly as the "lead driver".
"Pierre has been an immense asset for the team during this challenging period. I have been very impressed with his attitude, dedication and talent, and we look forward to continuing this project together for a long time," he said.
Gasly has had two teammates this season, with Australian Jack Doohan replaced by Argentine Franco Colapinto after six races. There is lingering uncertainty over who will partner the Frenchman next season.
Formula 1 is entering a new engine era in 2026, with considerable rules upheaval, but Briatore said Alpine were well prepared.
Alpine will switch to Mercedes engines next year, the same as used by the works team, reigning champions McLaren, and Williams.