Under the new structure, the two agencies will continue to operate separately and remain stand-alone brands, Publicis said.
Publicis Groupe chairman and chief executive Maurice Lévy said the new group would enable "both networks to maximise the potential of their creative resources at a global level".
Fallon president Pat Fallon, who will become Chairman Emiritus of the new group, said he would play an active role in the new group's direction. Fallon's Minneapolis headquarters will now report to the SSF Group.
Publicis also confirmed a number of high-level appointments. Robert Senior, a founding partner of Fallon London, becomes chief executive for the SSF Group in the UK, reporting to Roberts.
Jim O'Mahony will take up the post of CRIB (China, Russia, India and Brazil) chief executive. Simon Francis, previously EMEA managing director at media buying network OMD, will replace Jim O'Mahony as Saatchi's EMEA chief executive.
Both O'Mahony and Francis will report to Kevin Roberts.