“OZ” beauty MICHELLE WILLIAMS’ romance with actor Jason Segel was doomed by her undying love for the late HEATH LEDGER, sources say.

Michelle, 32, and Ledger had split by the time he died in January 2008 of a pre­scription drug overdose. But sources say she remains devoted to his memory as well as their daughter Matilda, 7.

“One of my favorite things to do is to imagine we would have reunited,” said the “My Week with Marilyn” star.

A source added: “Although she did her best to move on with Jason, Michelle has never stopped loving Heath.”

The former “Dawson’s Creek” cutie met “How I Met Your Mother” star Jason, 33, in early 2012, and he worked to win over both Michelle and her daughter.

“Jason adored Matilda,” said the source.

 “He was always buying her little gifts, reading stories to her at night and taking her places.”

In the fall, the couple moved into a rented apartment in Red Hook, N.Y., together. But the source says Michelle insisted on bringing along photos of Ledger, and the couple was often apart due to work commitments.

Then, in late October, their building was damaged by Hurricane Sandy, and the couple moved back into the apartment Michelle once shared with Ledger.

In January, Michelle told Jason she thought they should go their separate ways, said the source.

“Jason was heartbroken,” revealed the source. “But Michelle just never felt the kind of passion for him that she’d felt for Heath.”