Disgraced comic icon Bill Cosby will have to register as a sex offender in Massachusetts if he returns to his sprawling Shelburne Falls estate — and state and local authorities say they will be watching for him, the Herald has learned.

Pennsylvania’s Sexual Offenders Assessment Board recommended to a judge yesterday that Cosby be declared a “sexually violent predator.”

But the 81-year-old comedian’s conviction April 26 on three counts of aggravated indecent assault in Philadelphia is sufficient for Massachusetts authorities to require him to register here if he spends four days in one month or 14 days in a year in the Bay State, state officials confirmed yesterday.

Advocates applauded the news that a high-profile offender could face the same law as anyone else convicted of sex crimes.

“Having him on the registry is at least symbolic that he’s no longer above the law,” said attorney Wendy Murphy, a victims’ rights advocate. “He’ll be listed with the lowest of the low … where drugging his victim could land him a Level 3 rating.”

The Northwestern District Attorney’s Office confirmed yesterday that if Cosby fails to register upon his return, he’ll face prosecution.

Cosby and his wife, Camille, have spent much of the last four decades living on their secluded, wooded estate along the Deerfield River in Shelburne Falls, near the University of Massachusetts Amherst, where Cosby earned a master’s and a doctorate in education and was a fundraising co-chairman before UMass cut ties with him four years ago. The estate is worth more than $4 million — including a $2.6 million Colonial, circa 1800, according to assessors’ records. The property has an Olympic-sized pool, tennis court and is surrounded by rolling fields and woods, satellite images show.

The district attorney’s office in Philadelphia that prosecuted the onetime “America’s Dad” in April, is now asking the judge in the case to list the fallen comic as a predator and have his name added to Pennsylvania’s sex offender registry.

“We will see them in court,” said Andrew Wyatt, Cosby’s spokesman. A date for that showdown was not set.

Under Pennsylvania law, a sexually violent predator is defined as a person who has a mental abnormality or personality disorder that makes the person likely to engage in predatory sexually violent offenses.

The “I Spy,” “Fat Albert” and “The Cosby Show” star faces up to a decade in jail for drugging and assaulting former Temple University employee Andrea Constand at his home near Philadelphia in 2004.

His conviction came after a retrial that included testimony from five other women who accused the TV doctor of drugging and sexually abusing them. His lawyers said he plans to appeal.

Cosby has been ordered to stay at his Philly home and only leave to see a doctor or his lawyers. He’s also been fitted with a GPS monitoring bracelet.

But, if he is allowed to visit his bucolic home in Massachusetts before his sentencing, after parole or during an appeal, he will be legally required to submit his name and information to the Bay State’s Sex Offender Registry, an agency spokesman told the Herald yesterday.

“If I were to look up the definition of a sexually dangerous person, Bill Cosby would be at the top of the list,” Murphy said. “Based on common sense, he should be a Level 10.”

“When he’s free, he’s coming back,” Murphy added. “Talk among sex offenders is Massachusetts is the best state for them to live. But the registry is the great equalizer. He should have been on it all along.”

Herald wire services contributed to this report.