Japan's world number one Kaori Matsumoto overcame Corina Caprioriu to secure gold in the women's -57kg event.
The 2010 world champion - who now plans to retire - won it in golden score when the Romanian was disqualified for attacking through the back of the legs.
France's Automne Pavia, who
earlier defeated British hope Sarah Clark,
took one of the bronze medals with victory over Hedvig Karakas of Hungary.
Life after judo
Gold medal winner Kaori Matsumoto has said she plans to retire after London 2012 to take up a career as a judo coach, astronomer or pastry chef - she has yet to decide which
The other went to USA's Marti Malloy, who beat Giulia Quintavalle of Italy.
Malloy's win saw her become only the second American woman to claim an Olympic judo medal, matching Ronda Rousey's bronze in the -70kg category four years ago.
Clark, competing in her third Games, went out of the competition at the first hurdle, taking Pavia to golden score but losing to a Waza-ari half-point throw.
The South Shields player, who dropped down a weight after Beijing, initially felt she had turned out of the throw, but later accepted the move was legitimate.
"There is nothing more I could have done," she said. "In the fight, I made one small mistake which has unfortunately cost me possibly an Olympic gold medal."