Riner was born on 7 April 1989 in Les Abymes near Pointe-à-Pitre, in Guadeloupe, an insular region of France in the Caribbean.

[3] He received a bye into the second round of the competition before beating Anis Chedli of Tunisia and Kazakhstan's Yeldos Ikhsangaliyev to advance to the semi-finals.

[3] In the semis he was beaten by Uzbek judoka Abdullo Tangriev on the golden score, meaning Riner had to enter the repechage rounds.

He won bouts against Daniel McCormick, Vladimirs Osnachs, Ivan Iliev and Martin Padar in the pool stage before beating Marius Paškevičius in the semi-finals and Oscar Bryson in the final to take the gold medal.

After winning the +100 competition Riner was defeated by Daiki Kamikawa of Japan in the final of open weight class by a 2–1 judge's decision.

[13] At the 2011 World Judo Championships in Paris Riner won the gold medal in men's +100 kg division, beating Germany's Tölzer in the final.

[7][17][18] Riner was selected to compete for France at the 2012 Summer Olympics in London, England in the men's heavyweight event.

[22][23] At the 2020 Tokyo Olympics, Riner achieved a bronze medal in the over 100-kilogram class following a defeat by Russian judoka Tamerlan Bashaev.

[29] The following day in the mixed team event, France faced Japan in the gold medal match for the second straight Olympics.

Sanshiro Murao and Rika Takayama gave Japan an early 2–0 lead before Riner beat Tatsuru Saito.