Charles Oliveira and B.J. Penn show each other respect on Twitter

Charles Oliveira and B.J. Penn showed mutual respect for each other on social media on Tuesday night.

Oliveira first responded to a tweet saying that Penn was underrated by relatively newer fans of the sport who only took his 16-14-2 win-loss-draw record into consideration.

The reigning UFC lightweight titleholder called the Hall of Famer one of the best 155-pounders to ever compete inside the octagon.

"One of the best lightweight fighter to ever compete. PERIOD," said Oliveira.

See Charles Oliveira lauding B.J. Penn on Twitter below:

Penn also praised Oliveira in return and claimed he enjoyed watching the 32-year-old Brazilian superstar fight in the UFC.

"You’re the man @CharlesDoBronxs [call me hand emoji]. Absolutely love watching you compete [sunglasses smiley]," replied Penn.

Oliveira then thanked him for his kind words and ended the conversation by calling him a legend.

"Aloha BJ and Thank you! You can't imagine how significant are the words of a legend such as you," added Oliveira.

Here are a couple more exchanges between 'Do Bronx' and 'The Prodigy':

Penn is a former UFC lightweight and welterweight champion. He extended his career much past his prime, resulting in a seven-bout losing streak across three divisions.

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B.J. Penn is tied with three other fighters for the most successful UFC lightweight title defenses

B.J. Penn is tied with Frankie Edgar, Benson Henderson and Khabib Nurmagomedov as the UFC lightweight champions with the most successful title defenses at three.

Penn is also the first person to be inducted into the UFC Hall of Fame's modern-era wing and is the second-ever multi-division titleholder in the world's biggest MMA promotion after the legendary Randy Couture.

Find below the respective opponents Penn, Edgar, Henderson and Khabib defeated when they were the 155-pound weight class champs in the UFC:

Charles Oliveira, on the other hand, successfully defended his belt for the first time against fellow pound-for-pound ranked fighter Dustin Poirier at UFC 269 inside Las Vegas' T-Mobile Arena last month.

He is most likely to square off against No.1-ranked lightweight contender Justin Gaethje next, with a super showdown versus Irish sensation Conor McGregor also being rumored to be on the cards.