The former unified welterweight champion, 28, will face Monstro, 32, in a WBA title eliminator on October 11, 2025 at Wells Fargo Center in Philadelphia on DAZN.
Ennis said in a statement from Matchroom Boxing: “They can say what they want it don't make me a difference.
“These dudes can't tie my shoes. I'm the best in the world and they know it. I want all the big names and belts - the tour continues.”
Ennis will be moving up to the junior middleweight division having previously held the welterweight title from 2023.
After Terence Crawford left the division that year, Ennis was elevated to IBF champion and successfully defended the title twice in 2024 before defeating WBA titleholder Eimantas Stanionis in a unification bout that April in Atlantic City, New Jersey.
Lima said he was looking forward to “taking on the biggest challenge of [his] life” by fighting Ennis.
He said: “I am very excited to be taking on the biggest challenge of my life against a legit, world-level fighter in Ennis.
“I believe in myself ... we will be coming to war. Please don't take me lightly, Boots, as I am coming to win.”
After stopping Eimantas Stanionis in the sixth-round to become the WBA and IBF welterweight champion, Ennis chose not to defend his titles, and instead moved up to the junior middleweight division in an effort to get unification fights.
He previously said: “I’ve been making that weight for a long time and I feel like the time is right. It’s time for me to be comfortable and be myself.”
Ennis added he had chosen to move up a weight class in order to chase down more belts.
He explained: “What made me pivot is some of these other champions, they be taking other fights and things like that in between, and I just feel like I don’t have no time for that.
“My goal was to be having them back to back, fight champion after champion after champion and move up to 154. Like I always said in previous interviews, I’m down here for the belts.
“It’s time to move up, time to be me, time to be comfortable and not play a dangerous game going down to ‘47 ‘cause you got to be on point.
“You cutting weight, any miss, hiccup or anything like that, you can have an off night and I don’t want to have no off nights.”