Alonso joined Alpine on an initial one-year deal with an option for a second year that was widely expected to be activated after a solid return to F1 for the Spaniard.
Ahead of this weekend's Belgian Grand Prix, Alpine announced that Alonso had extended his contract and would be remaining with the team for next year, partnering Esteban Ocon.
"I'm very happy to confirm the contract extension with Alpine F1 Team into 2022," Alonso said.
"I felt at home the moment I returned to this team and have been welcomed back with open arms. It is a pleasure to work again with some of the brightest minds in our sport at Enstone and Viry-Chatillon.
"It's been a tricky season for everyone, but we've shown progress as a team and the result in Hungary serves as a good example of this progression. We're targeting more positive memories for the rest of this season but also crucially from next year onwards with the new regulation changes coming into Formula 1.
"I have been a big supporter of the need for a level playing field and change in the sport and the 2022 season will be a great opportunity for that. I am looking forward to the rest of this year and racing alongside Esteban in 2022 for Alpine."
Alonso struggled in the early part of the season as he got back up to speed, but has scored points in all of the last six races, including a run to fourth place in Hungary where he played an instrumental role in Ocon's shock victory.
"We are very pleased to confirm Fernando for next season, partnering with Esteban," said Alpine CEO Laurent Rossi.
"For us it is a perfect driver line-up, amongst the strongest on the grid. It works in a hugely complementary way, with both offering raw talent and speed, yet impeccable team spirit that delivered our first win in Hungary.
"Fernando has impressed us all since he returned to the sport at the beginning of this year. His dedication, teamwork and focus to extract the maximum from the team is incredible to be a part of and certainly special to witness.
"His performance in Hungary was another example of his racing pedigree and reminded everyone how skilled a driver he is."
Alonso returned to F1 ready to accept 2021 as being a year of transition ahead of the new technical regulations that will come into force for the 2022 season, offering Alpine a chance to make a step forward in performance.
Rossi expressed his confidence that Alonso's expertise would be critical in the development of the car and power unit for next season.
"I am convinced we can benefit strongly from Fernando's insight and experience as we enter the final development and optimisation phase of the 2022 chassis and power unit.," Rossi said.
"He is just as hungry as we are for success and is putting in every effort to translate it to performance.
"For now, however, we need to focus on delivering a strong second half of the year, extract the maximum at every race and ensure we finish as high up in the constructors' standings as possible.
"This will put us in a golden position for next year and the significant opportunity it brings."