A prominent Manhattan art collector says he was duped into selling a valuable bronze sculpture for a fraction of its value — and now wants $200 million from the lawyer who he says cheated him.

Stuart Pivar claims in a lawsuit filed in state Supreme Court on Tuesday that Park Avenue attorney John McFadden tricked him into selling Mademoiselle Pogani II, a piece by noted Romanian sculptor Constantin Brancusi, for a mere $100,000 — although it was worth “many times” that price.

The lawsuit does not list the actual value of the sculpture.

McFadden claimed he was just brokering a deal to sell the statue to Christie’s Auction House or the Philadelphia Art Museum, telling Pivar he was a trustee and representative of the museum — and that it would be “advantageous” to both men if the sale was made with the attorney listed as the owner.

He never mentioned he was fired from the Philadelphia museum for misconduct in 2014, the five-page court complaint alleges.

Pivar said McFadden even refused to let him see his prized sculpture when he sought “legitimate buyers” for the piece.

“The aforesaid conduct by (McFadden) constitutes a theft by deception and a fraud [from the beginning] … as it was never the intention of the defendant to offer the sculpture for sale to the museum, but rather to obtain ownership of the statue itself by deceit, misrepresentation and subterfuge,” the suit reads.

The 88-year-old art collector, who is representing himself, could not immediately be reached for comment. A man answering a phone number for McFadden declined to comment.

Pivar said McFadden told him the $100,000 was “necessary to consummate the sale to the museum,” and that he signed “the relevant contract” on May 16.

Just three days later, he said McFadden emailed him that “the deal was final and that the sculpture would remain in (McFadden’s) possession forever.”