By Chris Gallagher

RIO DE JANEIRO (Reuters) - The list of multiple-gold medalists in judo may be short but American Kayla Harrison never had any doubt that she would successfully defend her Olympic title.

At the Rio Games on Thursday, Harrison defeated France's Audrey Tcheumeo to become the first judoka to win two gold medals in the women's -78kg category, creating a legacy as one of the sport's all-time greats.

"I think it's really hard to repeat as an Olympic champion, I think it's one of the hardest things you can do," Harrison told reporters, lauding the job her coaches Jimmy Pedro and his father "Big Jim" did in getting her battle-ready.

"They pushed me to the point where when I showed up today, I knew that I had worked harder than everyone and no one was going to take it away from me."

Fearless -- like the name of the foundation she founded to support sexual abuse survivors like herself -- Harrison came out aggressive from the get-go and surged her way towards the final, shrugging off boos from a partisan crowd that was hoping for a gold for her longtime rival Mayra Aguiar of Brazil.

A final between Aguiar and Harrison, who held a 9-8 edge in their head-to-head record, would have been a dream match-up, but the Brazilian lost in the semi-finals and they never did meet on Thursday.

Instead, the 26-year-old American faced Tcheumeo in the clash for gold. Ahead on only penalties with seconds to go, she got her French opponent to submit on a hold for a match-ending ippon.

There has been much speculation over whether Harrison will compete in mixed martial arts but she declined to discuss her post-judo future in the immediate wake of her triumph.

"I'm just going to live in the moment and be Olympic champion," said Harrison, whose gold in London was the first by an American judoka.

But she left little doubt about whether she would continue in judo.

"I'm happy, I'm retiring. Two-time Olympic champion, that's it."

Aguiar and Slovenia's Anamari Velensek went on to take bronze.

Tcheumeo's silver, along with Cyrille Maret's bronze in the men's -100kg on Thursday, marked the third judo medal for France in Rio, but they remain without gold going into the final day of competition.

In the other men's medals, Lukas Krpalek of Czech Republic claimed gold, Azerbaijan's Elmar Gasimov won silver and Japan's Ryunosuke Haga won the other bronze.

(Editing by Frank Pingue, Bill Rigby and Mark Lamport-Stokes)