The challenge fight was officially announced by UFC President Dana White.
“The winner of this fight will fight Adesanya this year,” the head of the organization said in a video posted on social media. “And the title fight will take place in Sydney, Australia”
Robert Whittaker, 32, got his career back on track last September with a three-round unanimous decision over Marvin Vettori. Seven months earlier, the Australian made an unsuccessful attempt to take the championship belt from Israel Adesanya, losing to the Nigerian by unanimous decision in five rounds.
29-year-old South African Dricus Du Plessis is undefeated in the UFC, where he has already won five fights in a row, finishing in the last with a second-round technical knockout of Derek Brunson.
Robert Whittaker and Drycus Du Plessis currently sit second and sixth in the UFC middleweight rankings, respectively.