Covington suffered a suspected broken jaw during a closely fought contest in Las Vegas before Usman sealed a TKO win in the fifth and final round.
Usman blasted the challenger with two huge rights in the fifth, swarming his opponent with blows on the mat before referee Marc Goddard stopped the contest at four minutes and 10 seconds.
Bad blood had festered between Usman and Covington, the latter an outspoken Donald Trump supporter who has routinely courted controversy while describing himself as ‘the super villain of UFC’.
After the decision to stop the fight, Covington immediately sprinted out of the octagon backstage and later hit out at fight referee Goddard, calling him a “fake ref” and accusing him of ending the contest prematurely.
He wrote on Twitter: “I go in there to kill or be killed. You robbed me of that. You robbed the people of a fair fight. You should be ashamed of yourself.”
Usman extends his professional record to 16-1 and is now on an 11-fight winning streak in UFC. Birmingham’s Leon Edwards, ranked no.4 in the welterweight division, watched on from ringside and is hopeful of becoming Usman’s next challenger – with his only professional loss coming against the Nigerian Nightmare back in 2015.
Elsewhere on a stacked card, Alexander Volkanovski was crowned the new featherweight champion, outpointing Max Holloway after a near-perfect performance.
Amanda Nunes enhanced her reputation as the greatest fighter in women’s MMA history with victory over Germaine de Randamie.