Tanimoto (in white) made her decisive throw early on in the final
Japan's Ayumi Tanimoto became only the second woman to win successive Olympic judo golds after defeating France's Lucie Decosse in the 63kg category.
Tanimoto took hold of Decosse in the second minute, throwing her opponent over for an ippon and automatic win.
Holland's Elisabeth Willeboordse denied Cuba's Driulis Gonzalez her fifth Olympic medal, taking bronze along with North Korea's Won Ok-im.
Briton's Sarah Clark was earlier beaten by Austria's Claudia Heill.
The 30-year-old Clark had been ahead by waza-ari until she was caught off guard in the final 40 seconds to lose by ippon.
"I was quite confident going into my first fight, everything was right, perfect," said a tearful Clark.
"There weren't really any mistakes in my fight plan but I just got caught.
"I might have been on the back foot a tiny bit more than I should have been and then she just caught me with what she is probably best at."
Gonzalez, lightweight champion at the Atlanta Games in 1996, was penalised for passivity in extra time, handing Willeboordse the bronze.