One of the “Slender Man stabbers” — who viciously ambushed and hacked a classmate when she was 12 years old in an effort to please a made-up internet boogeyman — has vanished, and cops are now hunting her.

Morgan Geyser, 23, cut off her ankle monitor and escaped from the group home where she was living — and she’s currently on the run, according to cops in Madison, Wisconsin.

“Her whereabouts are unknown as of Sunday morning,” police said.

Geyser, along with her friend Anissa Weier, lured a fellow sixth-grade girl into a Waukesha, Wisconsin park in 2014 and stabbed her 19 times.

The attack was an effort to impress “Slender Man,” a supernatural character that rose to viral prominence on internet forums and was later the subject of a 2018 horror movie.

Miraculously, the victim survived the horrifying assault, crawling her way to safety until she was found by a passing bicyclist.

Geyser, as a 15-year-old, pleaded guilty to attempted first-degree murder in a deal that would see her put in a mental institution instead of serving jail time.

She spent nearly seven years in the Winnebago Mental Health Institute before a judge ordered her release in January.

In August, a group facility in Sun Prairie decided against admitting her due to a wave of negative publicity.

However police confirmed to WMTV that Geyser was staying at a group home in Madison.

She was last seen around 8 p.m. Saturday with an adult acquaintance, Madison cops said.

“We just heard the news that Morgan has walked away from the group home that she was housed at,” Geyser’s attorney, Tony Cotton, said in a video statement posted to social media.

“Obviously, it’s in her best interest to turn herself in immediately and not continue with this course of action,” Cotton said.

“We don’t know any of the facts about what happened or who might’ve assisted her. But certainly, if there is someone who might’ve assisted her, that person will be prosecuted to the fullest extent of the law,” he continued.

Cotton also issued a desperate plea for Geyser to turn herself in immediately to the authorities.

“If anybody has contact with Morgan, hears from her, or if Morgan happens to see this, turn yourself in,” Cotton added.

“Do not continue to remain on the run like this. It is not in your best interest to handle this matter that way,” he pleaded.