Heath Ledger’s former squeeze MICHELLE WILLIAMS sure know how to pick ‘em – her new BF DUSTIN YELLIN has a druggie past.

When Michelle  was spotted enjoying a sunny day in the park  with her daughter Matilda 7, and new boyfriendDustin Yellin, many believed things were looking up for the “MY Week With Marilyn” star.

 But Yellin has connections to the same hard-partying milieu that ultimately proved toxic for her great love, Heath Ledger, RadarOnline.com noted

Years ago, when he was just starting out in New York, Yellin was known for hosting wild parties at his loft at 136 10th Avenue.

 In February, 2000, Bijou Phillips stabbed Yellin in the leg during one out-of-control bash!

“We were hanging out with friends,” he explained at the time.

 “People were playing music. She picked up a kitchen knife and started chasing me with it. We were just horsing around, but it went too far. It was a moment of insanity.”

The wound almost proved fatal when Yellin suffered from internal bleeding days after being stitched up in the ER.

He was also famously involved with  Mary-Kate Olsen, a former Heath flame and doyenne of the downtown party scene.

And Yellin himself has admitted to drug use, claiming in an April 2013 video interview with the Tribeca Film Festival that “taking crazy hallucinogens” was one way he finds inspiration for his art.

Michelle, you've BEEN warned.