Silva raised her arms to the crowd in triumph as she beat Dorjsuren on a waza-ari, following a pulsating semi-finals victory that went into extra time against Romania's Corina Caprioriu.
Gold for Silva marks a fairytale rise to the Olympic podium from a childhood in Rio's notorious "City of God" favela, and provides redemption for a disappointing London 2012 when she was disqualified in the early rounds for a rule violation.
Rio 2016
Egyptian judoka sent home over handshake refusal with Israeli
15/08/2016 AT 19:51
Portugal's Telma Monteiro and Japan's Kaori Matsumoto won bronze.
Rio 2016
Egyptian booed for not shaking hands with Israeli
12/08/2016 AT 17:55
Rio 2016
Harrison defends title as women's -78kg champion
11/08/2016 AT 20:58