Betty Broderick, the woman who shot and killed her ex-husband and his new wife in cold blood, has died … TMZ has learned.

The California Department of Corrections and Rehabilitation tells TMZ … Betty was pronounced dead Friday morning.

We’re told Betty had been transported from the California Institution for Women prison to an outside medical facility back in April … and she died in the facility.

CDCR says the doctor who pronounced her dead determined she died from natural causes … though the San Bernardino County Coroner will determine her official cause of death.

Betty was serving a 32-year-to-life sentence for murdering Dan and Linda Broderick.

When Betty was married to Dan back in 1983, she confronted him … accusing him of having an affair with Linda, his 21-year-old assistant. Dan denied it for 2 full years, but ultimately moved out of the house and confessed to the affair.

The divorce was brutal … mostly over a custody war. Dan ended up getting full custody of their 4 kids.

In 1989, 7 months after Dan and Linda married, Betty stole a key from her daughter that opened the front door to Dan and Linda’s house, and then shot and killed the 2 of them.

Betty was sentenced to 2 consecutive, 15-year-to-life terms. She was also convicted of illegal use of a firearm.

Betty was denied parole 3 times. She was eligible again in 2032.