The deal took nobody by surprise, with Finland's 2007 world champion Kimi Raikkonen [ Images ] making way for the Spaniard next year at the Italian team who now have Spanish bank Santander as major backers.
Ferrari said the double world champion had agreed a three-year deal, with Spain's Marca newspaper saying Alonso would be paid around 20 million euros ($29.14 million) a year, some seven million less than Raikkonen was said to be getting.
That will force fellow Finn Heikki Kovalainen [ Images ] to look elsewhere.
Elsewhere, after a year that has already seen two drivers replaced and a third ruled out by injury, there is only uncertainty.
That deal may not be announced for some time however, with both Brawn drivers fighting for this year's world championship.
Brazilian Rubens Barrichello [ Images ], 15 points adrift of British team mate Jenson Button [ Images ], could go from Brawn to Williams to partner Germany's GP2 champion Nico Hulkenberg, who has been the team's reserve driver.
The autosport.com website on Wednesday quoted sources saying 37-year-old Barrichello had recently visited the Williams factory to discuss plans for next year.
Four new teams, and possibly five if BMW-Sauber are given the green light under new ownership, are also looking for drivers.
McLaren's Spanish test driver Pedro de la Rosa looks likely to be in the Campos GP cockpit while Brazilian Bruno Senna, nephew of the late triple champion Ayrton, is confident he will find a race seat.