The 20-year-old succeeds Yulia Barsukova (2000), Alina Kabayeva (2004) and Evgeniya Kanaeva (2008 and 2012) as the fourth consecutive Russian gymnast to wear the Olympic crown.
Concentrated from her fingernails to the tips of her toes, Mamun turned in four scores over 19 points -- the golden benchmark in Rhythmic Gymnastics -- in the final to finish ahead of the three-time World champion, who has been her greatest friend and rival.
Kudryavtseva, nicknamed "the Angel with Iron Wings" for her balletic style and steadfastness, came to Rio as the favorite for the title. As expected, the 18-year-old led at the halfway point of the competition but made a fatal mistake at the end of her Clubs routine when she missed a catch. It was her only error of the night, but it was serious enough to take her out of contention for the gold.
Mamun didn't miss her chance. She saved her best for last, delivering her highest score of the competition with the Ribbon to seal the gold. The first to greet her as she came off the floor was her personal coach Amina Zaripova, who 20 years ago finished fourth in this competition at the Olympic Games in Atlanta.
An Olympic medal at last for Rizatdinova
The Russian duel left just one podium spot up for grabs, and the three expected contenders -- Ukraine's Ganna Rizatdinova, Korea's Son Yeon Jae and Belarus's Melitina Staniouta -- went after it with all they had. After a slightly shaky start with the Hoop, it was Rizatdinova who grew stronger as the afternoon went on. In taking bronze four years after her disappointing 10th place finish in London, the two-time World medallist made good on her bid to win an Olympic medal.
Son, fifth in London, moved up a place in the ranking, a new best-ever finish for a Korean gymnast at the Olympic Games. As the 2015 World bronze medallist, Belarus's Melitina Staniouta began as a potential podium contender, but after two mistakes with the Clubs she could only shake her head at her fifth place finish.
Spain leads in Group qualification
Spain took its only Olympic title in Rhythmic Group Gymnastics in 1996, the first time the event was held at the Games. Twenty years later, the Spanish Group (Sandra Aguilar, Artemi Gavezou, Elena Lopez, Lourdes Mohedano and Alejandra Quereda) shimmied to first place in the qualification round in Rio Saturday, ahead of the Russians, whose team has won every Olympic gold since 2000.
The Russian Group (Anastastia Maksimova, Anastasia Tatareva, Maria Tolkacheva, Anastasia Bliznyuk and Vera Biriukova) led after the first of two routines (5 Ribbons), but turned in only the sixth best performance in their second exercise (2 Hoops/3 Pairs of Clubs), allowing the Spaniards to seize the lead by 0.233. Belarus (Hannah Dudzenkova, Maria Kadobina, Maryia Katsiak, Valeryia Pischelina and Arina Tsitsilina) finished third.
Italy, Japan, Israel, Bulgaria and Ukraine rounded out the eight Groups to qualify for Sunday's final, ejecting host nation Brazil, Germany, China, Uzbekistan, Greece and the United States.
FIG: The International Gymnastics Federation is the governing body for gymnastics worldwide. It is the oldest established international sports federation and has participated in the Olympic Games since their revival in 1896. The FIG governs seven disciplines: Gymnastics for All, Men's Artistic, Women's Artistic, Rhythmic, Trampoline, Aerobic and Acrobatic. It counts 142 national member federations and boasts a 28-person staff at its international seat in Lausanne (SUI), host city of the International Olympic Committee (IOC).