The Irishman’s stout business teamed up with Bare Knuckle FC to put on the show in Miami.
Promoting the event on social media, McGregor uploaded a video featuring four ring girls.
Each wearing Bare Knuckle-branded bikinis, they wore wide smiles for the camera.
One said: “We’re here at BKFC 57 and we love Forged Irish Stout”.
They each blew a kiss towards the camera before turning and striking a pose.
McGregor, 35, posted the video, writing: “Watching my inaugural @forgedirishstout bare knuckle event tonight in Miami!
“Thank you ladies.”
McGregor also uploaded a bizarre selfie in which he stared blank-faced at the screen, not offering even a hint of a smile.
One fan commented: “Dawg you have a wife and kids.”
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While a second wrote: “Oh you enjoying the show bruh.”
A third said: “Champ do what champ want.”
But a fourth asked: “What is that second picture?”
And another added: “Im stunned by this post idk what to react.”
McGregor has been with partner Dee Devlin since 2008, with the pair getting engaged in 2020.
They have four children together; Conor Jr, six, Croia, five, Rian, two and baby Mack, born in December.
McGregor has long been linked with a UFC return bout against Michael Chandler.
The duo missed out on a UFC 300 battle, however, and have seemingly been targeting a June date instead.
But recently asked if McGregor will in fact return in June, UFC president Dana White said: “No.
“When Conor’s ready to fight, you know we’ll announce it. That’s what we do.”