TMZ Sports talked to Couture -- one of the greatest fighters in UFC history -- about Jones, and his beef with the UFC's P4P rankings.
Of course, 33-year-old Jones has held down the #1 spot for a while, but was bumped earlier this week for the retired Khabib Nurmagomedov ... and has been beefin' with MMA fans over the decision online.
"I think if Jon really wants to solidify himself as pound-for-pound, he needs to go up to heavyweight and he needs to take a shot at winning that title. And, then that erases any argument that anybody could have."
Couture says Jon's dominated the light heavyweight division for so long ...but tells us winning in another division would take his career to a different level.