The 42-year-old Spaniard is in his second season at Aston Martin, which announced the extension on Thursday as a "multi-year" deal.

"I am at my physical best and still hungry. I will give my all as we continue our journey to becoming a world championship winning team," Alonso said in the announcement.

Alonso joined Aston Martin from Alpine to replace Sebastian Vettel after the German retired.

"We have built a strong working relationship over the last 18 months and we share the same determination to see this project succeed," Aston Martin team principal Mike Krack said.

The deal "takes us into 2026 when we begin our works power unit partnership with Honda", he added.

It will end speculation about Alonso's future after he had been linked to a possible move to Mercedes, who will lose Lewis Hamilton to Ferrari from next season.

"We have been in constant dialogue over the last few months and Fernando has been true to his word: when he decided he wanted to continue racing, he talked to us first," Krack said.

"Fernando has shown he believes in us, and we believe in him."

Alonso won his titles with Renault in 2005 and 2006. He took two years off in 2019 and 2020 to race in other series, including runs at the Indy 500.

"I said at the start of the year that I would decide if I wanted to continue racing first and then sit down with the team," he said.

"From the moment I joined the team in 2023 I felt extremely at home. In just over 15 months we have already achieved so much together, with some memorable podiums and battles."

Alonso had six podium finishes in the first eight races last season, when Aston Martin improved from seventh to fifth overall in the constructors' championship.

Australian Associated Press