Germany's Nick Heidfeld has signed a three-year contract to race for BMW's new Formula One team from next season, BMW announced on Friday.
Heidfeld, 28, said that the deal represented "the fulfilment of a big dream".
The German carmaker is taking over Swiss-based Sauber from January 2006 and entering their own team after supplying Williams with engines since 2000. Heidfeld is their first signing.
"We are very pleased that Nick will be with us in what will undoubtedly be a difficult initial phase," said BMW motorsport director Mario Theissen.
"He is not simply a fast and courageous driver, he is also an analytical and meticulous worker. Nick already knows the two sites in Munich and Hinwil and is familiar with everybody involved."
There was no word in the statement about Canadian Jacques Villeneuve, the 1997 world champion who has a year to run on his Sauber contract which he expects to be carried over.
Heidfeld's deal represents the culmination of a remarkable turnaround in the driver's fortunes and reunites him with old friends after three years at Sauber from 2001 to 2003.
"I'm not expecting a miracle during the first season after a new start in 2006," said Heidfeld. "But I'm confident that the new team will be successful over the long term."
Heidfeld, who finished second in Monaco and at the Nuerburgring this year, was in danger of being shut out of Formula One at the end of 2004 after a season of struggle with failing Jordan.
Williams stepped in, at BMW's recommendation, in January after a head-to-head test with Brazilian Antonio Pizzonia.
Pizzonia has replaced Heidfeld for the last two races in Italy and Belgium, with the German sidelined by a crash in testing in August and a bicycle accident last weekend, and will stand in again in Brazil next week.
Nico Rosberg, the Williams test driver and son of former world champion Keke, could also replace Heidfeld for the season-ending Japanese and Chinese races.
Williams had an option on Heidfeld's services for next season but that has now expired.
The team has Australian Mark Webber under contract and expect Briton Jenson Button to join them in 2006, although he is seeking to extricate himself from the contract so that he can stay with Honda-backed BAR.
Had Williams taken up the option on Heidfeld, Button could have argued that the team already had two race drivers under contract and no space for him.