Mia Farrow has gotten under the skin of Frank Sinatra’s fourth and final wife.

Barbara Sinatra angrily discounted reports that Ol’ Blue Eyes fathered a child out of wedlock with the “Rosemary’s Baby” actress.

The last Mrs. Sinatra, who married The Chairman of the Board in 1976 and stayed hitched until his 1998 death, called revelations about Ronan Farrow “a bunch of junk.”

“I can’t hardly believe that. It’s just a bunch of junk,” Barbara Sinatra told The Desert Sun newspaper.

“There’s always junk written — lies that aren’t true.”

Mia Farrow told Vanity Fair magazine that her son by Ronan is “possibly” Frank Sinatra’s kid.

The crooner and Mia Farrow were married for two years between 1966 and 1968, but remained close — perhaps really close — after their split.

Sinatra would have been about 71 if he had fathered Ronan Farrow in early 1987.

Ronan, 25, has long been described as the only biological child of Mia Farrow and scandalous moviemaker Woody Allen.

Mia Farrow, Ronan Farrow and Frank Sinatra all have blue eyes. Allen has brown eyes.

Barbara Sinatra, who lives near Palm Springs, Calif., appears to be at odds with one of Francis Albert’s kids, Nancy Sinatra.

The singer of “These Boots Are Made for Walkin’ ” — and fellow Palm Springs resident — stopped just short of calling Ronan a blood relative, but told Vanity Fair that he “is a big part of us, and we are blessed to have him in our lives.”

Still, 85-year-old widow Barbara Sinatra said she doesn’t believe a word of the Ronan-Frank talk.

She bluntly told the newspaper, “It sounds like a phony to me.”

A rep for Allen also dismissed the magazine story.

“The article is so fictitious and extravagantly absurd that he is not going to comment,” the rep said of the 77-year-old filmmaker, who infamously married Farrow’s adopted daughter Soon-Yi Previn.

Ronan, a Rhodes scholar and Yale Law School-educated attorney, has been staying above the fray and having a laugh over it.

He did it his way, yukking it up Wednesday with a tweet: “Listen, we’re all *possibly* Frank Sinatra’s son.”