A neurosurgeon and Rockland County mayor schemed to take control of a $5 million trust fund that he told his former wife he was setting up for their children, a lawsuit claims.

Ann Harrisburg married Dr. Jeffrey Oppenheim in 1992. The couple amassed $40 million in assets and Oppenheim was elected mayor of the Village of Montebello in 2007.

Harrisburg suggested setting up a trust fund for their children to avoid paying a hefty inheritance tax, according to her civil suit.

But Oppenheim designed the fund so that he could dole it out to a second wife or other kids, the suit says.

Then Oppenheim allegedly had an affair in 2012.

Oppenheim filed for divorce, and now Harrisburg is suing for half of the now $6 million trust, plus another $4 million in lost tax exemptions and legal fees.

Oppenheim’s lawyer, Kenneth Novenstern, told The Post, “The case was tried, and we’re waiting for a decision.”