The 50-year-old Spaniard, who was WRC champion in 1990 and 1992, is poised to bid for his second Dakar title in January.
"El Matador" will drive a 2WD Buggy California in the colours of Qatar in next year's event from Lima to Santiago.
Sainz, the 2010 winner, will join the past two champions Nasser Al-Attiyah and Stephane Peterhansel on the starting line in Peru on January 6.
"His return gives me great pleasure but is a serious threat," Peterhansel told AFP.
"This 2013 edition, with a confrontation between the last three winners, offers a very attractive display to the public and will be exciting," said the Frenchman who is chasing an 11th victory in the event.