WARSAW (AP) ― She was a Polish farmer’s daughter who emigrated to the United States, a maid who worked for a wealthy American heir, and a third wife who inherited much of the Johnson & Johnson fortune after a sensational court battle with her six stepchildren.

Barbara Piasecka Johnson, the widow of J. Seward Johnson Sr., heir to millions made from bandages, baby oil and pharmaceutical products, has died at age 76.

Johnson was best known for a nasty legal battle after her husband’s 1983 death, a feud that pitted her against his six children from two previous marriages. She largely prevailed, emerging with about $300 million from a fortune worth more than $500 million.

A resident of Monaco and one of the world’s richest women, Johnson used her wealth to become an art collector, amassing works by Rembrandt, Rubens, Gauguin and Raphael.

Her family announced her death Thursday in the Polish daily Rzeczpospolita, saying she died “after a long and serious illness” and that she will be buried April 15 in Wroclaw, the southwestern Polish city where she spent much of her youth.

Johnson died in Wroclaw, said Ricky Stachowicz, general counsel for BPJ Holding Corp., Johnson’s Princeton, New Jersey-based private real-estate holding company. The cause of death was not being disclosed at the request of her family, Stachowicz said.

Barbara Piasecka, who went by the diminutive “Basia,” was born in 1937 in Staniewicze, in an area of prewar eastern Poland that now lies in Belarus. Her family resettled after the war in Wroclaw, where she obtained a degree in art history.

She left communist Poland, studying for a time in Rome before arriving in 1968 in the United States with $100 and no knowledge of English. She got a job working as a cook and a maid in the Oldwick, New Jersey, estate of the Johnson & Johnson heir and his second wife of more than 30 years.

A year later, she left the family to take art courses at New York University, and Johnson Sr. rented an apartment for her in Manhattan and moved in with her.

In 1971, he divorced his second wife, the mother of two of his children, and married Piasecka eight days later. None of his children attended the wedding. At the time he was 76 and she was 34.

Johnson Sr., son of the founder of Johnson & Johnson, bequeathed most of his fortune of more than $500 million to Piasecka, largely excluding from his will both his children and Harbor Branch, an oceanographic research institute in Florida that he had founded.

The children contested the will, saying they did it on principle. They depicted their stepmother as a gold-digger who used fraud, threats and abuse to coerce her ailing 87-year-old husband into signing a new version of the will and said he was not of sound mind when he did so.

He signed it six weeks before he died of prostate cancer after having changed it many times in the preceding years, each time giving more and more of his estate to his third wife.

Johnson disputed the portrayal made by her husband’s children. She said her late husband chose to leave them out of his will because he had given them trust funds years earlier. She also argued that he didn’t want to leave them more money because he was disappointed by what she called their greed and “scandalous behavior.”

A settlement was reached in 1986 under which she kept more than $300 million, with the remaining going to Johnson Sr.’s children, the oceanographic institute, taxes and legal fees.

Johnson was not known in her homeland until the fall of communism in 1989, when she stepped in and offered millions of dollars to save the bankruptcy-threatened shipyard in Gdansk that had been the center of Nobel Peace Prize winner Lech Walesa’s pro-democracy Solidarity movement.

On one occasion she was given an enthusiastic welcome by workers at the massive shipyard, even though her plan to save it fell through.

A biography provided by her lawyer focused primarily on Johnson’s philanthropic and art-related activities. It noted that her paintings are loaned to museums worldwide and that she set up the Barbara Piasecka Johnson Foundation in 1974 to help the sick and needy, including people with autism.