The Italian team announced the deal on Thursday afternoon, less than 24 hours after initial reports of the move started to break.
Hamilton and Ferrari took advantage of a break clause in the Brit's contract with Mercedes - a contract signed just months ago - which allows him to opt out of the new deal after a single season.
There appears likely to be a break clause in his new Ferrari deal too, which the team described in a statement as 'multi-year'.
Ferrari's statement was light on details, just 20 words long, but Italian Formula 1 journalist Leo Turrini revealed further information on Sky Sport 24.
“It's the news of the millennium for F1," he said. "Hamilton signed a 2+1 contract, also with a view to 2026. Lewis dressed in red was a hypothesis that seemed to belong to the wildest dreams.
"We are in the presence of a historic event, such a successful driver has never arrived at Ferrari. Michael Schumacher had won two championships when he arrived. We are in the presence of something extraordinary. As Mogol writes: whether it will work or not, we will only find out by living."
That information from Turrini suggests that Hamilton will be in red until at least the end of the 2026 season, and at least a season longer if they impress him with their first car after the 2026 regulation changes.