Terms of the deal were not disclosed.
The move will bring the 23-year-old Altidore back to the EPL for the first time since 2009-10, when he spent an unhappy season with Hull City.
Altidore is coming off the best year of his career, after scoring 31 goals in all competitions -- a record goal total for an American in Europe -- helping AZ win the Dutch Cup, and being named to multiple Teams of the Season in the Netherlands.
Meanwhile, Sunderland, who are coached by fiery, controversial Italian Paolo Di Canio, finished 17th last season in the EPL. Di Canio did well to energize the side's survival fight last year when he took over late in the season, but the club will most likely be in the relegation discussion again this year.
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