Mary Kay Letourneau — the former teacher imprisoned after pleading guilty to raping her student, whom she later married — is dead after battling stage 4 colon cancer … 360aproko has learned.

Mary’s now-estranged husband, Vili Fualaau, previously shared her stage 4 cancer diagnosis on Instagram, sharing a photo of himself wearing a medical mask with the caption, “Praying for a miracle.”

Her attorney, David H. Gehrke, tells us Mary Kay had been in hospice care for the past month, and Vili had been by her side … helping take care of her.

Mary and Vili notoriously made headlines in the late ’90s, as she was 34, married and had 4 children when she began having sex with him — her 6th grade student. He was either 12 or 13 at the time.

She pled guilty in 1997 to 2 counts of felony second-degree rape of a child and ended up serving 7 years in prison.

Mary gave birth to 2 of Vili’s kids, and they wed in 2005 after she was released from prison. 360aproko broke the story … the couple split in 2017.

We contacted a spokesperson for Vili and they would only say it’s a very hard time right now.