It's champion vs. champion in the main event of UFC 284.

Saturday night's event is headlined by the two undisputed best in their weight classes, both of whom have meritorious claims at pound-for-pound No. 1.

The card in Perth, Australia, will be headlined by one of Australia's own in featherweight champion Alexander Volkanovski, who goes up in weight class to challenge lightweight titleholder Islam Makhachev of Dagestan.

It promises to be world-class fight, even in an era in which holding UFC gold doesn't necessarily mean you are the world's best in your weight class. To wit, heavyweight champion Francis Ngannou recently opted to become a free agent rather than accept the promotion's contract offer.

Volkanovski (25-1), based out of New South Wales, has a perfect record since entering UFC in 2016, with wins in all 12 of his Octagon matchups. He's used a style based on high-volume striking combined with seemingly limitless cardio, a strategy that brought him to the 145-pound championship, which he's successfully defended four times.

Makhachev (23-1), meanwhile, stumbled in his second UFC bout back in 2015. But he's been red hot since.

With a style that echoes his trainer, the legendary Khabib Nurmagomedov, Makhachev uses aggressive grappling to set up ruthless ground strikes as he works toward the finish. He's won 11 straight bouts.

Last time out, he submitted the UFC record holder for submission wins, Charles Oliveira, to claim the 155-pound title.

The evening's co-feature bout is an interim featherweight title bout, featuring Mexico's Yair Rodriguez (15-3, 1NC) vs. Josh Emmett (18-2) of Sacramento, Calif.

Both fighters love to get down and dirty, so anything but a wild scrap would be surprising.

Should Volkanovski win the lightweight title, the winner of the co-main would become the full-time featherweight champ. Should Volkanovski lose to Makhachev, the winner of Rodriguez vs. Emmett would get the next shot at Volkanovski at 145 pounds.

The bout marks the eighth fight between champions from different weight classes in UFC history. The most recent saw women's featherweight champion Amanda Nunes defeat Julianna Pena for the bantamweight belt at UFC 277.