"I believe that Jon Jones wants this fight," Ngannou tells us ... "I believe he'll want it to happen because it's gonna be a massive fight."

Ngannou looked fresh and happy when we spoke with him Monday morning -- sitting in front of his brand new UFC championship belt!

Of course, moments after he defeated Stipe Miocic at UFC 260 on Saturday night ... everyone began asking the obvious question -- when will Francis fight Jon Jones.

Jones went to social media with a message for the UFC -- "Show me the money."

Some people have suggested Jones is scared of Ngannou -- and he's using the money as an excuse to duck the new champ.

But, Ngannou doesn't believe that for a second -- saying he understands why Jon wants a massive payday ... and quite frankly, he hopes they BOTH get paid a ton of cash.

"He's been around so long and been champ for a long time so I think this might be the biggest fight of his career and mine."

"I think he wants to put something like this on his legacy, on his resume. I truly believe that he wants this fight to happen."

So, now the issue is working out a contract with UFC -- and fight fans all over the world ... as well as Francis himself, are hoping they can make a deal.

Francis says when the deal is signed, he knows he needs to beef up his wrestling game in order to defeat Jones -- a former college wrestling champion.

And, get this ... Ngannou says despite his dominant performance against Stipe, he's going back and watching the tape again because he feels there's real room for improvement.

Gotta be honest ... he looked pretty solid to us!

We also asked Francis how it feels to be the undisputed UFC heavyweight champ ... and watch the video, the guy is so proud!!!