Barbara Piasecka Johnson and her brother Gregor Piasecka pose in front of her mansion gate in Princeton, N.J., before hosting a press tour on July 23, 1986. (AP)

Barbara Piasecka Johnson, a former chambermaid who married into the Johnson & Johnson pharmaceutical family and walked away with part of its epic fortune after a bitterly contested battle over her husband’s will, died April 1 in Poland. She was 76.

Her office, BPJ Holdings, in Princeton, N.J., confirmed the death but did not disclose the cause. She was one of the world’s richest women and a longtime resident of Monaco.

The Polish-born Mrs. Johnson, known as Basia, in 1971 became the third wife of J. Seward Johnson, a son of J&J co-founder Robert Wood Johnson and a director of the New Brunswick, N.J.- based company for 50 years.

She was 34; he was 76 and had left his marriage of 32 years to be with her. They met in 1968, when she began working in his New Jersey home as a cook and chambermaid, according to an account in People magazine.

J. Seward Johnson’s death in 1983 sparked a legal battle in Surrogate’s Court in Manhattan between his six grown children and his widow over his will, which left her the bulk of his $500 million estate. In a 17-week trial in 1986 involving more than 200 lawyers, the children alleged that Mrs. Johnson had coerced her dying husband into changing his will to her benefit, according to a New York Times account.

Mrs. Johnson insisted that her husband’s children were blaming her for family rifts that predated her arrival.

“I’m very sorry these children are ridiculing their father,” she said during the trial, according to People. “They were out of the will long before I came to this country.”

The two sides reached a settlement that awarded $350 million to Mrs. Johnson and the rest to the children and to Harbor Branch, the oceanographic institute in Fort Pierce, Fla., that J. Seward Johnson had helped create.

In addition to the money, the agreement gave Mrs. Johnson possession of the mansion she had built and shared with her husband — a 46,000-square-foot Georgian-style villa on 140 acres in a wooded section of Princeton they called Jasna Polana, Polish for “bright meadow.”

She turned the property into a private golf club with a course designed by professional golfer Gary Player. The Johnson mansion served as the clubhouse.

Mrs. Johnson resettled in Monaco and became an art collector and philanthropist. In March, Forbes magazine estimated her net worth to be $3.6 billion, making her one of the 50 richest women in the world.

In 2004, Prince Hans-Adam II of Liechtenstein, founder of Vienna’s Liechtenstein Museum, paid $36.7 million for a Florentine cabinet auctioned in London by Mrs. Johnson, making it the most expensive piece of furniture ever sold at auction.

Made of ebony, gilt-bronze and precious stones, the so-called Badminton cabinet was originally crafted for Henry Somerset, the third Duke of Beaufort, by the grand ducal workshops in Florence in the 18th century.

In 2009, Mrs. Johnson sold Rembrandt’s 1658 “Portrait of a Man With Arms Akimbo” for a record $32.9 million, to a bidder later identified as Las Vegas casino developer Steve Wynn.

In 1990, Mrs. Johnson said she might spend as much as $100 million to revive the Gdansk Shipyard in Poland, which a decade earlier had spawned the Solidarity resistance movement to communism in Eastern Europe. Her proposed involvement proved too difficult to carry out.

Barbara Piasecka was born Feb. 25, 1937, in Staniewicze, Poland. She earned degrees in art history from the University of Wroclaw and immigrated to the United States from Rome in 1968, arriving with $100 and speaking little English.

She went to work for J. Seward Johnson and his second wife, the former Esther Underwood, at their estate in Oldwick, N.J. She left after nine months to study English in Manhattan, at which point Johnson dispatched his chauffeur to bring her to his New Jersey office, where he professed his love, according to People.

“I never expect it, because we could hardly talk to each other,” she later said, the magazine reported. Together they began assembling a collection of paintings by Monet, Picasso, Rembrandt, Titian and other artists.

Through the Princeton-based Barbara Piasecka Johnson Foundation, Mrs. Johnson supported Polish students in the United States and humanitarian projects in Poland, among other causes. In recent years she focused on providing help to children and young adults with autism.

— Bloomberg News