Tom Tagholm, the head of creative at 4Creative, the channel's in-house creative department, will become the acting creative director of Channel 4. The company will not immediately seek a replacement and Foraker will remain as a consultant to the channel from his base in Los Angeles.
Foraker was responsible for the rebrand of Channel 4 in 2005, for which he won a D&AD black Pencil and Campaign's Advertiser of the Year, as well as the idents for E4, More4 and Film4.
David Abraham, the chief executive of Channel 4, said: "Brett is one of the most influential creative talents of his generation. He has delivered consistently innovative work across our channels."
Foraker will maintain a base in England, where he is represented for commercials by RSA.