The late screen icon follows in the recent footsteps of Faye Dunaway and Juliette Binoche in having her image used to promote the event.
Based on a photo by Otto L. Bettmann (©Corbis/Bettmann), the poster was created by Bronx agency (Paris), who will design all the graphics for this year's Cannes.
"50 years after her death, Marilyn is still a major figure in world cinema, an eternal icon, whose grace, mystery and power of seduction remain resolutely contemporary," the Festival said.
"Each of her screen appearances sparks the imagination. The Festival poster captures Marilyn by surprise in an intimate moment where myth meets reality - a moving tribute to the anniversary of her passing, which coincides with the Festival anniversary.
"She enchants us with this promising gesture: a seductively blown kiss. The Festival is a temple of glamour and Marilyn is its perfect incarnation. Their coming together symbolises the ideal of simplicity and elegance."
Last month, actor and director Nanni Moretti was named as the president of the jury for the 2012 Cannes Film Festival.
Last year's jury was headed by Robert De Niro. The festival awarded 2011's Palme D'Or to Terrence Malick's The Tree of Life.
The 2011 event also saw the world premiere of The Artist, which swept the board at this year's Oscars.