Conor McGregor has challenged Justin Gaethje after his knockout win over Dustin Poirier by vowing to 'slap him around'.

The Notorious called out the American after he became the second BMF champion in history in his rematch with Poirier at UFC 291.

Gaethje knocked out his opponent in Round 2 with a spectacular head kick in Salt Lake City to avenge his 2018 defeat and claim the symbolic BMF title - the 'baddest motherf****r'.

In doing so, he set himself up to tackle the winner of October's lightweight title bout between Islam Makhachev and Charles Oliveira.

But McGregor was full of brawn after Gaethje became the BMF champion, tweeting: 'Justin, I’ll slap you around' - throwing his fight with Michael Chandler into doubt. 

In a tweet minutes later, he added: 'I’m the real bmf, he can fight for pennies if he wants but I want spirits, I call the shots, I’m in it to launch shots, f*** Chandler, you want it call for it.' 

He is supposed to return to the octagon in December in an unconfirmed fight against Chandler, but his latest tweet has caused fans to wonder about his intentions. 

Gaethje is yet to collide with McGregor despite their long careers at the top. 

Chandler congratulated The Highlight on his achievement on Twitter before reacting to McGregor, saying 'This guy' and 'Just pee in the cup @TheNotoriousMMA it ain’t that complicated….', in a reference to the two negative drug tests that McGregor needs to return to the US Anti-Doping Agency to be able to fight again.

Other fighters reacted to his staggering victory. 

Meanwhile, Brian 'Boom' Kelleher tweeted: 'Gaethje has improved so much as a calculated killer now. Head shot dead'.

Lando Vannata said: 'When the foot wraps around the cerebellum…goodnight', complemented with a dozing face emoji.