A masterpiece by the late graffiti-art legend Jean-Michel Basquiat is at the center of a Manhattan family feud rife with charges of betrayal, abuse and a death-bed change to a will.

Investor Hubert Neumann, 86, claims his adult daughter went behind his back and got his wife to sign over the rights to the multimillion-dollar work “Flesh and Spirit” while she was “receiving serious medical treatment” in 2015, according to court records.

Neumann — whose wife, Dolores, died of liver cancer in September 2016 — says his 51-year-old daughter, Belinda, is now trying to sell the 12-foot-by-12-foot painting at Sotheby’s for $30 million — and he’s suing to stop the auction, which is set for next week.

“Sotheby’s broke its promise to Hubert Neumann and prioritized short-term profit and prestige over its contractual obligations,” said his lawyer Andrew G. Celli Jr. of Emery Celli Brinckerhoff & Abady.

Neumann says his daughter, who is an art gallerist, strong-armed her mother into changing the will so that it gives her the right to 80 percent of the painting’s proceeds.

The reason given for the change in the will is that Belinda “does not have financial stability on her own or through her husband and has three children to support.”

The will gives eldest daughter. Kristina Neumann, 53, just 10 percent and a third daughter, Melissa Neumann, 48, the other 10 percent plus $1 million because “she has a wealthy husband.”

Finally Dolores, who was friends with Basquiat in the 1980s, disinherited her husband in the new will, explaining: “He has been physically abusive.”

Hubert told The Post, “I’m not accepting the fact that I did anything like that to her.”

His Manhattan Supreme Court suit says it is not legal to disinherit a spouse under New York law.

Melissa said she plans to contest the document in Surrogate’s Court. Belinda and her attorney did not return calls for comment.

A Sotheby’s spokeswoman said, “This 11th-hour claim is entirely without merit, and we are confident that the court will find in our favor and the auction will proceed as scheduled.”