Ronaldo Mota Sardenberg (born on (1940-10-08)October 8, 1940 in Itu, Brazil) is a Brazilian diplomat and politician.

He was the Chargé d'affaires of Brazil to the Soviet Union in 1982; and Ambassador in Moscow from 1985 to 1989.

He was also the Representative of Brazil at the United Nations Security Council from 1993 to 1994; and President of the UNSC in October 1993.

As Minister for Special Projects, he had been in charge of nuclear and space-related policies.

He also served as Secretary for Strategic Affairs of the Presidency of the Republic, from 1995 to 1998.