TikTok star Megan Eugenio -- AKA "Overtime Megan" -- is adamantly denying she took a picture in bed with Antonio Brown ... saying flat-out, the person in the snap "is not me."

A picture of the controversial ex-NFL superstar laying alongside a mystery woman made the rounds on social media this week ... which appeared to be a post on his personal Snapchat.

Given the person's appearance, fans of the sports personality initially speculated Megan was the one cozying up with A.B. ... but on Wednesday, she put an end to the rumors.

"I cannot believe I have to say this but that is not me," Eugenio said on Instagram alongside several crying laughing emojis.