Newey said in May he was leaving champions Red Bull in search of new challenges.
The 2025 season is due to start on March 16th with the Australian Grand Prix in Melbourne and is the last championship before the sport enters a new engine era and major rules revamp in 2026.
Cars designed by the Briton have won 25 drivers' and constructors' championships for Williams, McLaren and Red Bull. His 2023 Red Bull was the most dominant car in the sport's history with 21 wins from 22 races.
Newey was also sought by rival teams, including title contenders Ferrari and McLaren. No details were given of his salary or shareholding but media reports have indicated Newey will be paid some 20 million pounds a year.
Owned by Canadian Lawrence Stroll, the Aston Martin team have 43-year-old double world champion Fernando Alonso and Stroll's son Lance as their drivers and an ambitious plan to get to the top.
"I am thrilled to be joining the Aston Martin Aramco Formula 1 team," Newey said in a statement. "I have been hugely inspired and impressed by the passion and commitment that Lawrence brings to everything he is involved with.
"Lawrence is determined to create a world-beating team. He is the only majority team owner who is actively engaged in the sport.
"They have all the key pieces of infrastructure needed to make Aston Martin a world championship-winning team and I am very much looking forward to helping reach that goal."
Newey told the BBC last year that he regretted never having worked with Alonso, and that is also a box he can now tick.
Stroll Sr. has spent heavily on the team, expanding the factory into a new campus facility and bringing in top talent from rivals.
Former Mercedes engine head Andy Cowell was announced in July as new chief executive officer, replacing former McLaren boss Martin Whitmarsh. Aston have also recruited former Ferrari technical director Enrico Cardile.
Aston Martin, currently fifth in the standings, are starting an exclusive new partnership with Honda, Red Bull's current engine supplier, from 2026.
"This is huge news. Adrian is the best in the world at what he does - he is at the top of his game," said Stroll in a statement.
"It’s the biggest story since the Aston Martin name returned to the sport and another demonstration of our ambition to build a Formula One team capable of fighting for world championships."
Stroll said he had been determined to sign Newey as soon as the designer became available and initial conversations confirmed the interest was mutual.
"Adrian is a racer and one of the most competitive people I have ever met," he added.
"When he saw what we have built at Silverstone... he quickly understood what we are trying to achieve. We mean business, and so does he."
